Salt, photoresist composition and method for producing photoresist pattern

ABSTRACT

A salt represented by formula (I): 
                         
wherein Q 1 , Q 2 , L 1 , W, and Z + are defined in the specification.

This nonprovisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2011-172729 filed in JAPAN on Aug. 8, 2011,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a salt, a photoresist composition and amethod for producing a photoresist pattern.

BACKGROUND OF THE INVENTION

A photoresist composition to be used for semiconductor usually comprisesa salt as an acid generator.

US2007/0122750A mentions a salt represented by the following formula asan acid generator.

(wherein X represents monocyclic or polycyclic hydrocarbon group having3 to 30 carbon atoms or the like, Q¹ and Q² each independently representa fluorine atom or a C1-C6 perfluoroalkyl group, and A⁺ represents anorganic cation).

SUMMARY OF THE INVENTION

The present invention relates to the followings:

-   <1> A salt represented by formula (I);

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group,

-   L¹ represents a C1-C20 trivalent aliphatic saturated hydrocarbon    group in which a hydrogen atom bonded to a methylene group of    aliphatic saturated hydrocarbon chain moiety can be replaced by a    fluorine atom or a hydroxy group and in which a methylene group can    be replaced by an oxygen atom, —NR²— or a carbonyl group, where R²    represents a hydrogen atom or a C1-C6 alkyl group,-   the hydroxyl group of L¹-OH is positioned on the aliphatic    saturated, hydrocarbon chain moiety of L¹,-   W represents a C3-C36 alicyclic hydrocarbon group-   in which a methylene group can be replaced by an oxygen atom, a    sulfur atom, a carbonyl group or a sulfonyl group, and in which a    hydrogen atom can be replaced by a hydroxy group, a C1-C12 alkyl    group, a C1-C12 alkoxy group, C3-C18 alicyclic hydrocarbon group or    C6-C14 aromatic hydrocarbon group, and-   Z⁺ represents an organic cation.-   <2> The salt according to <1>, wherein the moiety L¹-OH of    formula (I) is represented by formula (L¹-1)

wherein X⁰ represents a single bond,

-   a C1-C14 divalent aliphatic hydrocarbon group which can have a    fluorine atom or a hydroxy group, or a group represented by formula    (a-1)    -A¹⁰    X¹⁰-A¹¹    _(s)X¹¹-A¹²-*  (a-1)    where s represents an integer of 0 or 1, X¹⁰ and X¹¹ each    independently represent an oxygen atom, a carbonyl group, a    carbonyloxy group, or an oxycarbonyl group, A¹⁰, A¹¹ and A¹² each    independently represent a C1-C12 divalent aliphatic hydrocarbon    group which can have a fluorine atom or a hydroxy group, *    represents a binding position to a carbon atom,-   X¹ represents —O-*¹, —NR²-*¹, —O—CO-*¹, —O—CH2-*¹, —O—CH₂—CO—O-*¹ or    —NR²—CH₁-*¹ where *¹ represents a binding position to W,-   *⁰ represents a binding position to a carbon atom binding to Q¹ and    Q², and m¹ represents an integer of 0 to 6.-   <3> The salt according to <2>, wherein X¹ represents —O-*¹, —NR²-*¹,    —O—CO-*¹, —O—CH₂-*¹, or —NR²—CH₂-*¹ where *¹ represents a binding    position to W.-   <4> The salt according to any one of <1> to <3>, wherein Z′ is a    triarylsulfonium cation.-   <5> A photoresist composition, which comprises the salt according to    any one of <1> to <4> and a resin which is hardly soluble or    insoluble but soluble in an aqueous alkali solution by action of an    acid.-   <6> The photoresist composition according to <5>, which further    comprises a basic compound.-   <7> A process for producing a photoresist pattern comprising the    following steps (1) to (5):    -   (1) a step of applying the photoresist composition according to        <5> or <6> on a substrate,    -   (2) a step of forming a photoresist film by conducting drying,    -   (3) a step of exposing the photoresist film to radiation,    -   (4) a step of baking the exposed photoresist film, and    -   (5) a step of developing the baked photoresist film, thereby        forming a photoresist pattern.

The salt of the present invention can give a photoresist compositionwhich can provide a photoresist pattern without profile of a dummypattern but with fine profile even when optical proximity correction isadopted to a process for producing photoresist pattern by using a maskwith a dummy pattern.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates cross-section views of photoresist patterns.

DESCRIPTION OF PREFERRED EMBODIMENTS

The salt of the present invention is represented by the formula (I).Hereinafter, such salt is sometimes referred to as “SALT (I)”.

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group,

-   L¹ represents a C1-C20 trivalent aliphatic saturated hydrocarbon    group in which a hydrogen atom bonded to a methylene group of    aliphatic saturated hydrocarbon chain moiety can be replaced by a    fluorine atom or a hydroxy group and in which a methylene group can    be replaced by an oxygen atom, —NR²— or a carbonyl group, where R²    represents a hydrogen atom or a C1-C6 alkyl group, the hydroxy group    of L¹-OH is positioned on the aliphatic saturated hydrocarbon chain    moiety of L¹,-   W represents a C3-C36 alicyclic hydrocarbon group-   in which a methylene group can be replaced by an oxygen atom, a    sulfur atom, a carbonyl group or a sulfonyl group, and in which a    hydrogen atom can be replaced by a hydroxy group, a C1-C12 alkyl    group, a C1-C12 alkoxy group, C3-C18 alicyclic hydrocarbon group or    C6-C14 aromatic hydrocarbon group, and-   Z⁺ represents an organic cation.

Hereinafter, the moiety corresponding to the part except Z⁺ in formula(I) and having a negative charge is sometimes referred to as “sulfonicacid anion”.

The perfluoroalkyl group represented by Q¹ or Q² includes atrifluoromethyl group, a pentafluoroethyl group, a heptafluoropropylgroup, a heptafluoroisopropyl group, a nonafluorobutyl group, anonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group and a perfluorohexyl group. Q¹ and Q² eachindependently represent preferably a fluorine atom and a trifluoromethylgroup, more preferably a fluorine atom.

The C1-C20 trivalent aliphatic saturated hydrocarbon group representedby L¹, which may be a linear or branched chain, or an alicyclichydrocarbon group, includes

-   a C1-C20 alkanetriyl group such as a methine group, a    ethan-1,1,2-triyl group, a propane-1,2,3-triyl group,    butane-1,2,4-triyl group, a pentane-1,2,5-triyl group, a    pentane-1,3,5-triyl group, a hexane-1,2,6-triyl group, a    hexane-1,3,6-triyl group, a heptane-1,2,7-triyl group, a    heptane-1,3,7-triyl group, an octane-1,2,8-triyl group, an    octane-1,3,8-triyl group, group, an octane-1,4,8-triyl group, a    nonane-1,2,9-triyl group, a nonane-1,3,9-triyl group, a    nonane-1,4,9-triyl group, a decane-1,2,10-triyl group, a    decane-1,3,10-triyl group, a decane-1,4,10-triyl group, a    decane-1,5,10-triyl group, an undecane-1,2,11-triyl group, an    undecane-1,3,11-triyl group, an undecane-1,4,11-triyl group, an    undecane-1,5,11-triyl group, a dodecane-1,2,12-triyl group, a    dodecane-1,3,12-triyl group, a dodecane-1,4,12-triyl group, a    dodecane-1,5,12-triyl group, a dodecane-1,6,12-triyl group, a    tridecane-1,2,13-triyl group, a tridecane-1,2,13-triyl group, a    tridecane-1,3,13-triyl group, a tridecane-1,4,13-triyl group, a    tridecane-1,5,13-triyl group, a tridecane-1,6,13-triyl group, a    tetradecano-1,2,14-triyl group, a tetradecane-1,3,14-triyl group, a    tetradocane-1,4,14-triyl group, a tetradecane-1,5,14-triyl group, a    tetradecano-1,6,14-triyl group, a tetradecane-1,7,14-triyl group, a    pentadeoane-1,2,15-triyl group, a pentadecane-1,3,15-triyl group, a    pentadecane-1,4,15-triyl group, a pentadecane-1,5,15-triyl group, a    pentadecane-1,6,15-triyl group, a pentadecane-1,7,15-triyl group, a    hexadecane-1,2,16-triyl group, a hexadecane-1,3,16-triyl group, a    hexadecane-1,4,16-triyl group, a hexadecane-1,5,16-triyl group, a    hexadecane-1,6,16-triyl group, a hexadecane-1,7,16-triyl group, a    hexadecane-1,8,16-triyl group, a heptadecane-1,2,17-triyl group, a    heptadecane-1,3,17-triyl group, a heptadecane-1,4,17-triyl group, a    heptadecane-1,5,17-triyl group, a heptadecane-1,6,17-triyl group, a    heptadecane-1,7,17-triyl group, and a heptadecane-1,8,17-triyl    group; and-   trivalent alicyclic hydrocarbon groups having a structure in which    three hydrogen groups have been removed from the group represented    by formula (KA-1), (KA-2), (KA-3), (KA-4), (KA-5), (KA-6), (KA-7),    (KA-8), (KA-9), (KA-10), (KA-11), (KA-12), (KA-13), (KA-14),    (KA-15), (KA-16), (KA-17), (KA-18), (KA-19), (KA-20), (KA-21) or    (KA-22).

The C1-C20 trivalent aliphatic saturated hydrocarbon group may be aC4-C20 trivalent hydrocarbon group which consists of C1-C17 alkanediylgroup and a trivalent alicyclic group or a C4-C20 hydrocarbon groupwhich consists of an alkanetriyl group and a divalent alicyclichydrocarbon group.

Examples of the C1-C17 divalent saturated hydrocarbon group include aC1-C17 linear alkanediyl group such as a methylene group, an ethylenegroup, a propane-1,3-diyl group, a propane-1,2-diyl group, abutane-1,4-diyl group, a butane-1,3-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a heptane-1,7-diyl group, anoctane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diylgroup, a undecane-1,11-diyl group, a dodecane-1,12-diyl group, atridecane-1,13-diyl group, a tetradecane-1,14-diyl group, apentadecane-1,15-diyl group, a hexadecane-1,16-diyl group, aheptadecane-1,17-diyl group, an ethane-1,1-diyl group, apropane-1,1-diyl group and a propane-2,2-diyl group; a C2-C17 branchedalkanediyl group such as a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group; a divalentmonocyclic saturated hydrocarbon group such as a cyclobutane-1,3-diylgroup, a cyclopentane-1,3-diyl group, a cyclohexane-1,2-diyl group, a1-methylcyclohexane-1,2-diyl group, a cyclohexane-1,4-diyl group, acyclooctane-1,2-diyl group and a cyclooctane-1,5-diyl group; a divalentpolycyclic saturated hydrocarbon group such as a norbornane-2,3-diylgroup, a norbornane-1,4-diyl group, a norbornane-2,5-diyl group, anadamantane-1,2-diyl group, an adamantine-1,5-diyl group and anadamantane-2,6-diyl group; and a group formed by combining two or moregroups selected from the group consisting of the above-mentioned groups.

Methylene groups of the aliphatic saturated hydrocarbon represented byL¹ can be replaced by an oxygen atom, —NR²— where R² represents ahydrogen atom or a C1-C6 alkyl group, or a carbonyl group. Consideringeasiness of producing the SALT (I), L¹ is preferably the aliphaticsaturated hydrocarbon in which a methylene group has been replaced by anoxygen atom, —NR²— where R² represents a hydrogen atom or a C1-C6 alkylgroup, or a carbonyl group. When L¹ represents the aliphatic saturatedhydrocarbon wherein a methylene group has been replaced by an oxygenatom, —NR²— where R² represents a hydrogen atom or a C1-C6 alkyl group,or a carbonyl group, the moiety L¹-OH of formula (I) includes a divalentgroup represented by formula (L¹-1).

wherein X⁰ represents a single bond,

-   a C1-C14 divalent aliphatic hydrocarbon group which can have a    fluorine atom or a hydroxy group, or-   a group represented by formula (a-1)    -A¹⁰    X¹⁰-A¹¹    _(s)X¹¹-A¹²-*  (a-1)    where s represents an integer of 0 or 1, X¹⁰ and X¹¹ each    independently represent an oxygen atom, a carbonyl group, a    carbonyloxy group, or an oxycarbonyl group, A¹⁰, A¹¹ and A¹² each    independently represent a C1-C12 divalent aliphatic hydrocarbon    group which can have a fluorine atom or a hydroxy group,-   * represents a binding position to a carbon atom, X¹ represents    —O-*¹, —NR²-*¹, —O—CO-*¹, —O—CH₂-*¹, —O—CH₂—CO—O-*¹ or —NR²—CH₂-*¹,    preferably —O-*¹, —NR²-*¹, —O—CO-*¹, —O—CH₂-*¹ or —NR²—CH₂-*¹, where-   *¹ represents a binding position to W and R² represents a hydrogen    atom or a C1-C6 alkyl group, and-   *⁰ represents a binding position to a carbon atom binding to Q¹ and    Q², and-   m¹ represents an integer of 0 to 6.

The C1-C14 divalent aliphatic hydrocarbon group represented by X⁰includes

-   a C1-C14 alkylene group such as a methylene group, an ethylene    group, a propane-1,3-diyl group, a propane-1,2-diyl group, a    butane-1,4-diyl group, a butane-1,3-diyl group, a pentane-1,5-diyl    group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an    octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl    group, a undecane-1,11-diyl group, a dodecane-1,12-diyl group, a    tridecane-1,13-diyl group, a tetradecane-1,14-diyl group; and a    C3-C14 saturated cyclic hydrocarbon group such as a    cyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, a    cyclohexane-1,2-diyl group, a 1-methylcyclohexane-1,2-diyl group, a    cyclohexane-1,4-diyl group, a cyclooctane-1,2-diyl group and a    cyclooctane-1,5-diyl group, a norbornane-2,3-diyl group, a    norbornane-1,4-diyl group, a norbornane-2,5-diyl group, an    adamantane-1,2-diyl group, an adamantane-1,5-diyl group, an    adamantane-2,6-diyl group.

The C1-C12 divalent aliphatic hydrocarbon group represented by A¹⁰, A¹¹and A¹² includes

-   a C1-C12 alkylene group such as a methylene group, an ethylene    group, a propylene group, a butylene group, a pentylene group, a    hexylene group, a heptylene group, an octylene group, a decylene    group, a dodecylene group; and-   a C3-C12 divalent saturated cyclic hydrocarbon group such as a    cyclopropylene group; cyclobutylene group, cyclopentylene group,    cyclohexylene group, a cycloheptylene group, a cyclooctylene group,    a cyclononylene group, a cyclodecylene group, a norbornylene group,    an amadantylene group and an isonorbnornylene group.

X⁰ is preferably a single bond, C1-C4 alkylene group, or a grouprepresented by formula (a-1) where s is 0, A¹⁰ is an adamantane ring,

X¹¹ is a carbonyloxy group and A¹² is C1-C4 alkylene group.

The C1-C6 alkyl group represented by R² includes a methyl group, anethyl group, a propyl group, a butyl group, a pentyl group, and a hexylgroup.

X¹ is preferably —O—CO-*¹ or —O—CH₂—CO—O-*¹ where *¹ represents abinding position to W as defined above.

The symbol “*” and “*” is alternatively used in the present application.

The divalent group represented by formula (L¹-l) includes the followingones;

where *⁰ represents a binding position to a carbon atom binding to Q¹and Q², R² is the same as defined above, and *¹ represents a bindingposition to W.

In formula (I), the hydroxy group of L¹-OH is positioned on thealiphatic saturated hydrocarbon chain moiety of L¹.

In the trivalent aliphatic saturated hydrocarbon group represented byL¹, a hydrogen atom bonded to a methylene group of aliphatic saturatedhydrocarbon chain moiety can be replaced by a fluorine atom or a hydroxygroup.

Herein, the term “aliphatic saturated hydrocarbon chain moiety” means achain alkylene group which constitutes the trivalent aliphatic saturatedhydrocarbon group represented by L¹.

When L¹ represents a C1-C20 trivalent aliphatic saturated hydrocarbongroup in which a hydrogen atom has been replaced by a fluorine atom,L¹-OH includes the following ones;

where *⁰ represents a binding position to a carbon atom binding to Q¹and Q², and *¹ represents a binding position to W.

The alicyclic hydrocarbon group represented by W includes a monocyclicalicyclic hydrocarbon group and a polycyclic alicyclic hydrocarbongroup.

The monocyclic alicyclic hydrocarbon group includes C3-C36 cycloalkylgroups such as groups in which one hydrogen atom has been removed fromany one of the cycloalkanes represented by formulae (KA-1) to (KA-7) asmentioned above.

The polycyclic alicyclic hydrocarbon group includes apolycyclic groupssuch as groups in which one hydrogen atom has been removed from any oneof the cycloalkanes represented by formulae (KA-8) to (KA-22) asmentioned above.

In the alicyclic hydrocarbon group represented by W, a methylene groupcan be replaced by an oxygen atom, a sulfur atom, a carbonyl group or asulfonyl group, and a hydrogen atom can be replaced by a hydroxy group,a C1-C12 alkyl group, a C1-C12 alkoxy group, C3-C18 alicyclichydrocarbon group or C6-C14 aromatic hydrocarbon group.

The alkyl group includes a methyl group, an ethyl group, a propyl group,an isopropyl group, a butyl group, a pentyl group, a hexyl group, aheptyl group, an octyl group, a decyl group, and a dodecyl group.

The alkoxy group includes a methoxy group, an ethoxy group, a propoxygroup, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxygroup, an octyloxy group, a decyloxy group, and a dodecyloxy group.

The C3-C18 alicyclic hydrocarbon group includes a monocyclic alicyclichydrocarbon group such as C3-C12 cycloalkyl groups (e.g. a cyclopentylgroup, a cyclohexyl group, a methylcyclohexyl group, adimethylcyclohexyl group, a cycloheptyl group and a cyclooctyl group);and a polycyclic alicyclic hydrocarbon group such as a decahydronaphthylgroup, an adamantyl group, a norbornyl group.

The aromatic hydrocarbon group includes a phenyl group, a naphthylgroup, an anthryl group, biphenyl group, phenanthryl group, fluorenylgroup.

Specific examples of W include the following groups.

W includes preferably an adamantyl group, a norbornane group or acycloalkyl group, more preferably an adamantyl group. Herein, theadamantyl group preferred as W includes one in which a methylene grouphas been replaced by carbonyl group, and in which an adamantyl group inwhich a hydrogen atom has been replaced by a hydroxy group.

Specific examples of the sulfonic acid anion include the followinggroups.

In the formula (I), Z⁺ represents an organic cation.

Examples of the organic cation represented by Z⁺ include an organiconium cation such as an organic sulfonium cation, an organic iodoniumcation, an organic ammonium cation, a benzothiazolium cation and anorganic phosphonium cation.

As the organic cation represented by Z⁺, an organic sulfonium cation andan organic iodonium cation are preferable, and an organic cationrepresented by formulae (b2-1), (b2-2) (b2-3) and (b2-4) is morepreferable.

wherein R^(b4), R^(b5) and R^(b6) independently represent a C1-C30aliphatic hydrocarbon group in which a hydrogen atom can be replaced bya halogen atom, a hydroxy group, C1-C12 alkoxy group, or C6-C18 aromatichydrocarbon group; a C3-C18 alicyclic hydrocarbon group in which ahydrogen atom can be replaced by a halogen atom, a C2-C4 acyl group or aglycidyloxy group; a C6-C18 aromatic hydrocarbon group in which ahydrogen atom can be replaced by a halogen atom, a hydroxy group, C3-C18alicyclic hydrocarbon group, or C1-C12 alkoxy group; or R^(b4) andR^(b5) are bonded each other together with the adjacent sulfur atom toform a C3-C18 saturated or unsaturated, nonaromatic or aromatic ring;

-   R^(b7) and R^(b8) are independently in each occurrence a hydroxy    group, a C1-C12 alkyl group or a C1-C12 alkoxy group,-   m2 and n2 independently represents an integer of 0 to 5,-   R^(b9) and R^(b10) each independently represent a C1-C18 alkyl group    or a C3-C18 alicyclic hydrocarbon group; or R^(b9) and R^(b10) are    bonded each other to form a C2-C10 divalent acyclic hydrocarbon    group which forms a 3- to 12-membered ring, preferably 3- to    7-membered ring together with the adjacent —S⁺—, and one or more    —CH₂— in the divalent acyclic hydrocarbon group can be replaced by    an oxygen atom, sulfur atom or carbonyl group;-   R^(b11) represents a C1-C18 alkyl group, a C3-C18 alicyclic    hydrocarbon group, or C6-C18 aromatic hydrocarbon group;-   R^(b12) represents a C1-C18 alkyl group; a C3-C18 alicyclic    hydrocarbon group; C6-C18 aromatic hydrocarbon group in which a    hydrogen atom can be replaced by C1-C12 alkyl group, C1-C12 alkoxy    group, C3-C18 alicyclic hydrocarbon group, or C1-C12    alkylcarbonyloxy group;-   or the group in which the alkyl group has been combined with the    aromatic hydrocarbon group; or R^(b11) and R^(b12) are bonded each    other to form a C2-C10 divalent acyclic hydrocarbon group which    forms a 2-oxocycloalkyl group together with the adjacent —CHCO—, and    one or more —CH₂— in the divalent acyclic hydrocarbon group can be    replaced by an oxygen atom, sulfur atom or carbonyl group, R^(b13),    R^(b14), R^(b15), R^(b16),R^(b17) and R^(b18) independently    represent a hydroxy group, a C1-C12 aliphatic hydrocarbon group or a    C1-C12 alkoxy group,-   L^(b11) represents a sulfur atom or an oxygen atom, and-   o2, p2, s2 and t2 each independently represents an integer of 0 to    5,-   q2 and r2 each independently represents an integer of 0 to 4, and u2    represents 0 or 1.

As the aliphatic hydrocarbon group represented by R^(b4), R^(b5) andR^(b6), preferred are a C1-C18 alkyl group in which a hydrogen atom canbe replaced by a hydroxy group, or a C1-C12 alkoxy group, a C6-C18aromatic hydrocarbon group.

The aliphatic hydrocarbon group represented by R^(b9) or R^(b10)includes preferably a C1-C12 alkyl group. The alicyclic hydrocarbongroup represented by R^(b9) or R^(b10) is preferably C4-C12, alicyclichydrocarbon group.

Preferable examples of the alkyl group represented by R^(b4) to R^(b6)include a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, a sec-butyl group, a tert-butyl group, a pentylgroup, a hexyl group, an octyl group, a decyl group, a dodecyl group, ahexadecyl group, a pentadecyl group, a heptadecyl group and an octadecylgroup, and more preferable examples thereof include a methyl group, anethyl group, a propyl group and a butyl group. Preferable examples ofthe alicyclic hydrocarbon group represented by R^(b4) to R^(b6) includea cyclopropyl group, a cyclobutyl group, a cyclopentyl group, acyclohexyl group, a cycloheptyl group, a cyclodecyl group, an adamantylgroup, a 2-alkyladamantyl-2-yl group, a 1-tadaman-2-yl)alkane-1-yl groupand an isobornyL group, and more preferable examples thereof include acyclopentyl group and a cyclohexyl group. Preferable examples of thearomatic group represented by R^(b4) to R^(b6) include a phenyl group, anaphthyl group and an anthryl group, and a phenyl group is morepreferable. Examples of the C1-C12 alkoxy group include a methoxy group,an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, ahexyloxy group, a heptyloxy group, an octyloxy group, a decyloxy groupand a dodecyloxy group. Examples of the halogen atom include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom. Examples ofthe C2-C4 acyl group include an acetyl group, a propyonyl group and abutyryl group.

Preferable examples of the alkyl group represented by R^(b7) and R^(b8)include a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, a sec-butyl group, a sec-butyl group, a pentylgroup, a hexyl group, an octyl group and a 2-ethylhexyl group. Examplesof the C1-C12 alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Preferable examples of the alkyl group represented by R^(b9) to R^(b12)include a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, a sec-butyl group, a tert-butyl group, a pentylgroup, a hexyl group, an octyl group and a 2-ethylhexyl group. Suchalkyl group preferably has 1 to 12 carbon atoms. Preferable examples ofthe alicyclic hydrocarbon group represented by R^(b9) to R¹¹ include acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, a cyclodecyl group, a 2-alkyl-2-adamantylgroup, a 1-(1-adamantyl)-1-alkyl group and an isobornyl group.Preferable examples of the aromatic group represented by R^(b12) includea phenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-tertbutylphenyl group, 4-cyclohexylphenyl group, 4-methoxyphenyl group,biphenyl group and a naphthyl group, and a phenyl group is morepreferable.

Preferable examples of the group in which the alkyl group has beencombined with the aromatic hydrocarbon group represented by R^(b12)include an aralkyl group such as benzyl group.

Preferable examples of the alkylcarbonyloxy group represented by R^(b12)include a group consisting of an acyl group and an oxygen atom.

Examples of the C3-C12 divalent acyclic hydrocarbon group formed bybonding R^(b9) and R^(b10) include a trimethylene group, atetramethylene group and a pentamethylene group. Examples of the ringgroup formed together with the adjacent S⁺ and the divalent acyclichydrocarbon group include a thiolan-1-ium ring (tetrahydrothipheniumring), a thian-1-ium ring and a 1,4-oxathian-4-ium ring. A C3-C7divalent acyclichydrocarbon group is preferable.

Examples of the C1-C10 divalent acyclic hydrocarbon group formed bybonding R^(b11) and R^(b12) include a methylene group, an ethylenegroup, a trimethylene group, a tetramethylene group and a pentamethylenegroup and examples of the ring group include oxocyclopentane ring,oxocyclonexane ring, oxonorbornane ring and oxoamadantane ring. A C1-C5divalent acyclic hydrocarbon group is preferable.

Examples of the group in which the alkyl group has been combined withthe aromatic hydrocarbon group include typically an aralkyl group,preferably benzyl group,

As examples of the organic cations represented by formulae (b2-1) to(b2-4) include organic cations mentioned in JP2010-204646A1.

As the organic action represented by Z⁺, an arylsulfonium cation ispreferred, and a triarylsulfonium cation is more preferred.

Among the above-mentioned cations, the organic cations represented byformulae (b2-1) (b2-2) and (b2-3) are preferable, and the organiccations represented by formula (b2-1) are more preferable.

As the organic cations represented by formula (b2-1), more preferred isthe cation represented by the formula (b2-1) in which any of R^(b4),R^(b5) and R^(b6) is an aromatic hydrocarbon group, still more preferredis the cation represented by the formula (b2-1-1), especially morepreferred is triphenylphosphonium cation or tritolylsulfonium cation.

wherein R^(b19), R^(b20) and R^(b21) are independently in eachoccurrence a halogen atom (preferably a fluorine atom); a hydroxy group;a C1-C18 aliphatic hydrocarbon group in which a hydrogen atom can bereplaced by a halogen group, a C2-C4 acyl group, or a grycidyloxy group;or a C1-C12 alkoxy group; and R^(b19) and R^(b20), R^(b19) and R^(b21)or R^(b20) and R^(b21) can be bonded each other to form a ring togetherwith S⁺, and v2, w2 and x2 independently each represent an integer of 0to 5.

The aliphatic hydrocarbon group of R^(b19), R^(b20) and R^(b21) includesan alkyl group and an alicyclic hydrocarbon group, preferably C1-C12alkyl group and C4-C18 alicyclic hydrocarbon group.

The alkyl group represented by R^(b19), R^(b20) and R^(b21) ispreferably a C1-C12 alkyl group such as a methyl group, an ethyl group,a propyl group, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, an octyl group and a2-ethylhexyl group.

The alicyclic hydrocarbon group represented by R^(b19), R^(b20) andR^(b21) is preferably a C4-C18 alicyclic hydrocarbon group such as acyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptylgroup, a cyclodecyl group, an adamantyl group, a 2-alkyladamantyl-2-ylgroup, a 1-(adaman-2-yl)alkane-1-yl group and an isobornyl group.

Each of R^(b19), R^(b20) and R^(b21) is preferably a halogen atom(preferably a fluorine atom), a hydroxy group, a C1-C12 alkyl group anda C1-C12 alkoxy group, and more preferably a halogen atom (preferably afluorine atom) and a C1-C6 alkyl group.

Preferably, the v2, w2 and x2 independently each represent 0 or 1.

Examples of the cation represented by the formula (b2-1-1) include thefollowing ones.

The organic cations represented by formula (b2-2) include the followingones.

The organic cations represented by formula (b2-3) include the followingones.

The SALT (I) consists of any one of the sulfonic acid anions asmentioned above and any one of the organic cation as mentioned above.

Specific examples of SALT (I) include those shown in Tables 1, 2, 3 and4. In each table, the symbols, e.g. “(Ia1-1-1)”, in the columns“Sulfonic acid anion” represent the sulfonic acid anions represented bythe above-mentioned formulae corresponding to the symbols, and thesymbols, e.g. “(b2-c-1)”, in the columns “Organic cation” represent theorganic cations represented by the above-mentioned formulaecorresponding to the symbols.

TABLE 1 SALT (I) Sulfonic acid anion Organic cation (I-1) (Ia1-1-1)(b2-c-1) (I-2) (Ia1-1-2) (b2-c-1) (I-3) (Ia1-1-3) (b2-c-1) (I-4)(Ia1-1-4) (b2-c-1) (I-5) (Ia1-1-5) (b2-c-1) (I-6) (Ia1-1-6) (b2-c-1)(I-7) (Ia1-1-7) (b2-c-1) (I-8) (Ia1-1-8) (b2-c-1) (I-9) (Ia1-1-9)(b2-c-1) (I-10) (Ia1-1-10) (b2-c-1) (I-11) (Ia1-1-1) (b2-c-10)

TABLE 2 SALT (I) Sulfonic acid anions Organic cation (I-12) (Ia1-1-2)(b2-c-10) (I-13) (Ia1-1-3) (b2-c-10) (I-14) (Ia1-1-4) (b2-c-10) (I-15)(Ia1-1-5) (b2-c-10) (I-16) (Ia1-1-6) (b2-c-10) (I-17) (Ia1-1-7)(b2-c-10) (I-18) (Ia1-1-8) (b2-c-10) (I-19) (Ia1-1-9) (b2-c-10) (I-20)(Ia1-1-10) (b2-c-10) (I-21) (Ia1-1-1) (b2-c-14) (I-22) (Ia1-1-2)(b2-c-14) (I-23) (Ia1-1-3) (b2-c-14) (I-24) (Ia1-1-4) (b2-c-14) (I-25)(Ia1-1-5) (b2-c-14) (I-26) (Ia1-1-6) (b2-c-14) (I-27) (Ia1-1-7)(b2-c-14) (I-28) (Ia1-1-8) (b2-c-14) (I-29) (Ia1-1-9) (b2-c-14) (I-30)(Ia1-1-10) (b2-c-14) (I-31) (Ia1-1-1) (b2-c-23) (I-32) (Ia1-1-2)(b2-c-23) (I-33) (Ia1-1-3) (b2-c-23) (I-34) (Ia1-1-4) (b2-c-23) (I-35)(Ia1-1-5) (b2-c-23) (I-36) (Ia1-1-6) (b2-c-23) (I-37) (Ia1-1-7)(b2-c-23) (I-38) (Ia1-1-8) (b2-c-23) (I-39) (Ia1-1-9) (b2-c-23) (I-40)(Ia1-1-10) (b2-c-23) (I-41) (Ia1-1-1) (b2-c-27) (I-42) (Ia1-1-2)(b2-c-27) (I-43) (Ia1-1-3) (b2-c-27) (I-44) (Ia1-1-4) (b2-c-27) (I-45)(Ia1-1-5) (b2-c-27) (I-46) (Ia1-1-6) (b2-c-27) (I-47) (Ia1-1-7)(b2-c-27) (I-48) (Ia1-1-8) (b2-c-27) (I-49) (Ia1-1-9) (b2-c-27) (I-50)(Ia1-1-10) (b2-c-27) (I-51) (Ia1-1-1) (b2-c-28) (I-52) (Ia1-1-2)(b2-c-28)

TABLE 3 SALT (I) Sulfonic acid anions Organic cation (I-53) (Ia1-1-3)(b2-c-28) (I-54) (Ia1-1-4) (b2-c-28) (I-55) (Ia1-1-5) (b2-c-28) (I-56)(Ia1-1-6) (b2-c-28) (I-57) (Ia1-1-7) (b2-c-28) (I-58) (Ia1-1-8)(b2-c-28) (I-59) (Ia1-1-9) (b2-c-28) (I-60) (Ia1-1-10) (b2-c-28) (I-61)(Ia1-1-1) (b2-c-31) (I-62) (Ia1-1-2) (b2-c-31) (I-63) (Ia1-1-3)(b2-c-31) (I-64) (Ia1-1-4) (b2-c-31) (I-65) (Ia1-1-5) (b2-c-31) (I-66)(Ia1-1-6) (b2-c-31) (I-67) (Ia1-1-7) (b2-c-31) (I-68) (Ia1-1-8)(b2-c-31) (I-69) (Ia1-1-9) (b2-c-31) (I-70) (Ia1-1-10) (b2-c-31) (I-71)(Ia1-1-1) (b2-c-2) (I-72) (Ia1-1-2) (b2-c-2) (I-73) (Ia1-1-3) (b2-c-2)(I-74) (Ia1-1-4) (b2-c-2) (I-75) (Ia1-1-1) (b2-c-6) (I-76) (Ia1-1-2)(b2-c-6) (I-77) (Ia1-1-3) (b2-c-6) (I-78) (Ia1-1-4) (b2-c-6) (I-79)(Ia1-1-1) (b2-c-15) (I-80) (Ia1-1-2) (b2-c-15) (I-81) (Ia1-1-3)(b2-c-15) (I-82) (Ia1-1-4) (b2-c-15) (I-83) (Ia1-1-1) (b2-c-18) (I-84)(Ia1-1-2) (b2-c-18) (I-85) (Ia1-1-3) (b2-c-18) (I-86) (Ia1-1-4)(b2-c-18) (I-87) (Ia1-1-1) (b2-c-30) (I-88) (Ia1-1-2) (b2-c-30) (I-89)(Ia1-1-3) (b2-c-30) (I-90) (Ia1-1-4) (b2-c-30) (I-91) (Ia1-1-11)(b2-c-1) (I-92) (Ia1-1-12) (b2-c-1) (I-93) (Ia1-1-13) (b2-c-1) (I-94)(Ia1-1-14) (b2-c-1) (I-95) (Ia1-1-11) (b2-c-10) (I-96) (Ia1-1-12)(b2-c-10)

TABLE 4 SALT (I) Su1fonic acid anions Organic cation (I-97) (Ia1-1-13)(b2-c-10) (I-98) (Ia1-1-14) (b2-c-10) (I-99) (Ia1-1-11) (b2-c-14)(I-100) (Ia1-1-12) (b2-c-14) (I-101) (Ia1-1-13) (b2-c-14) (I-102)(Ia1-1-14) (b2-c-14) (I-103) (Ia1-1-11) (b2-c-23) (I-104) (Ia1-1-12)(b2-c-23) (I-105) (Ia1-1-13) (b2-c-23) (I-106) (Ia1-1-14) (b2-c-23)(I-107) (Ia1-1-11) (b2-c-27) (I-108) (Ia1-1-12) (b2-c-27) (I-109)(Ia1-1-13) (b2-c-27) (I-110) (Ia1-1-14) (b2-c-27) (I-111) (Ia1-1-11)(b2-c-28) (I-112) (Ia1-1-12) (b2-c-28) (I-113) (Ia1-1-13) (b2-c-28)(I-114) (Ia1-1-14) (b2-c-28) (I-115) (Ia1-1-11) (b2-c-31) (I-116)(Ia1-1-12) (b2-c-31) (I-117) (Ia1-1-13) (b2-c-31) (I-118) (Ia1-1-14)(b2-c-31)

The SALT (I) includes preferably salts in which Q¹ and Q² is a fluorineatom; the moiety L¹-OH is represented by formula (L-1); and W is anadamantyl group in which a methylene group can be replaced by a carbonylgroup and in which a hydrogen atom can be replaced by a hydroxy group,or a C1-C12 alkyl group.

In the SALT (I), the moiety L¹-OH is preferably represented by formula(L-1) in which X⁰ is a single bond, C1-C4 alkylene group, or a grouprepresented by formula (a-1) where s is 0, A¹⁰ is an adamantane ring,X¹¹ is a carbonyloxy group and A¹² is C1-C4 alkylene group, X¹represents —O—CO-*¹ or —O—CH₂—CO—O-*¹ where *¹ represents a bindingposition to W as defined above.

Examples of preferred SALT (I) include specifically the saltsrepresented by formulae (I-1), (I-2), (I-3), (I-4), (I-11) (I-12),(I-13), (I-14), (I-21), (I-22), (I-23), (I-24), (I-31), (I-32), (I-33),(I-34), (I-41), (I-42), (I-43) (I-44), (I-51), (I-52) (I-53), (I-54),(I-61), (I-62), (I-63), (I-64), (I-91), (I-92), (I-93), (I-94), (I-95),(I-96), (I-97), (I-98), (I-99), (I-100), (I-101), (I-102), (I-103),(I-104), (I-105), (I-106), (I-107), (I-108), (I-109), (I-110) (I-111),(I-112), (I-113), (I-114), (I-115), (I-116), (I-117), and (I-118).

The process for producing SALT (I) will be illustrated,

The SALT (I) in which the moiety “L¹-OH” represents the followingformula

can be produced by reacting a salt represented by formula (I1-a) with acompound represented by formula (I1-b), in the presence of a catalystsuch as silver oxide or silver perchloride, in a solvent such as anorganic solvent, e.g., chloroform, dichloromethane, dichloroethane,methanol, dimethylformamide or acetonitrile, as shown below;

wherein Q¹, Q², W and Z⁺ are defined as above, and the formula (I1)represents the SALT (I) in which the moiety L¹-OH is represented by theformula:

The salt represented by formula (I1-b) includes the following ones,which can be prepared by reacting the compound represented by W—COOH,where W is as defined above, with 1,1′-carbodiimidazole in an organicsolvent such as chloroform.

The salt represented by formula (I1-a) can be produced by reacting3,3-dimethyl-2,4-dioxacyclopentylmethanol with a salt represented byformula (I1-d) in a solvent such as an organic solvent, e.g.,chloroform, followed by treating the compound represented by formula(I1-e) with an acid, e.g. oxalic acid, as shown below;

wherein Q¹, Q² and Z⁺ are defined as above.

The salt represented by formula (I1-d) can be produced by reacting asalt represented by formula (I1-f) with 1,1′-carbonyldiimidazole in asolvent such as an organic solvent, e.g., chloroform, as shown below;

wherein Q¹, Q² and Z⁺ are defined as above.

The salt represented by formula (I1-f) can be produced by a methoddescribed in JP2008-127367.

The SALT (I) wherein the moiety “L¹-OH” of formula (I) represents thefollowing formula

can be produced by reacting a salt represented by formula (I2-a) with acompound represented by formula (I1-b), in the presence of a catalystsuch as silver oxide or silver perchloride, in a solvent such as anorganic solvent, e.g., chloroform, dichloromethane, dichloroethane,methanol, dimethylformamide or acetonitrile, as shown below;

wherein Q¹, Q², W and Z⁺ are defined as above, and the formula (I2)represents the SALT (I) in which the moiety L¹-OH is represented by theformula;

The salt represented by formula (I2-a) can be produced by reacting acompound represented by formula (I2-c) with a salt represented byformula (I1-d) in a solvent such as an organic solvent, e.g.,chloroform, followed by treating the compound represented by formula(I2-e) with an acid, e.g. oxalic acid, as shown below;

wherein Q¹, Q², W and Z⁺ are defined as above.

The compound represented by formula (I2-c) can be produced by reacting acompound represented by formula (I2-f) in the presence of a reducingagent such as sodium borohydrate in a solvent such as an organicsolvent, e.g., acetonitrile, as shown below;

The compound represented by formula (I2-f) can be produced by reacting acompound represented by formula (I2-g) with 1,1′-carbonyldiimidazole ina solvent such as an organic solvent, e.g., chloroform, followed byreacting the obtained a compound represented by formula (I2-i) with3,3-dimethyl-2,4-dioxacyclopentylmethanol in a solvent such as anorganic solvent, e.g., chloroform, shown as follows.

The compound represented by formula (I2-g) is available on the market.

The SALT (I) wherein the moiety “L¹-OH” of formula (I) represents thefollowing formula, hereinafter such salt is referred to as the salt (I3)

can be produced by reacting a salt represented by formula (I2-a) with acompound represented by formula (I3-a), in the presence of a base suchas pyridine, in a solvent such as an organic solvent, e.g., chloroformor acetonitrile, as shown below;

wherein Q¹, Q², W and Z⁺ are defined as above, and the formula (I3)represents the SALT (I) in which the moiety L¹-OH is represented by theformula:

The compound represented by formula (I3-a) includes the following ones,which are available on the market.

The SALT (I) in which the moiety “L¹-OH” is represented by the formula(L¹-1) can be produced by the same methods described above.

Hereinafter, the photoresist composition of the present invention willbe illustrated.

The photoresist composition comprises SALT (I) and a resin which ishardly soluble or insoluble but soluble in an aqueous alkali solution byaction of an acid.

The SALT (I) works as an acid generator in the photoresist composition.The photoresist composition of the present invention may comprise otheracid generators than the SALT (I). The photoresist composition maycomprise, if necessary, a basic compound which is a quencher known inthe art, and a solvent.

The other acid generators than the SALT (I) include known acidgenerators. The other acid generators than SALT (I) may be either ionicor non-ionic one

The other acid generators than SALT (I) may be a salt comprisingdifferent cation and anion from those of SALT (I), or a salt comprisingthe same cation as SALT (I) and a different known anion from that ofSALT (I).

The other acid generators than the SALT (I) include those represented byformula (B1-1), formula (B1-2), formula (B1-3), formula (B1-4), formula(B1-5), formula (B1-6), formula (B1-7), formula (B1-8), formula (B1-9),formula (B1-10), formula (B1-11), formula (B1-12), formula (B1-13),formula (31-14), formula (B1-15), formula (B1-16), formula (B1-17),formula (B1-18), formula (B1-19) and formula (B1-20). Among them,preferred are compounds having triphenylsulfonium cation and compoundshaving tritolylsulfonium cation, and more preferred are compoundsrepresented by formula (B1-1), formula (B1-2), formula (B1-3), formula(B1-6), formula (B1-7), formula (B1-11), formula (B1-12), formula(B1-13) and formula (B1-14).

The resin for the photoresist composition of the present invention ishardly soluble or insoluble but soluble in an aqueous alkali solution byaction of an acid. With such resin as having the above-mentionedproperties, the photoresist composition can give a photoresist patternby an acid generated from the acid generator as mentioned above.

Herein, “soluble in an aqueous alkali solution by the action of an acid”means such property as soluble in an aqueous alkali solution bycontacting it with into an acid while hardly soluble or insoluble in anaqueous alkali solution before contacting it with into an acid.

The resin for the photoresist composition of the present invention hasan acid-labile group. Such resin can be produced by polymerizing one ormore kinds of monomers having an acid-labile group. Hereinafter, theresin having an acid-labile group is sometimes referred to as “rein(A)”.

Herein “an acid-labile group” refers to a group capable of being cleavedin case of contacting with an acid to give a hydrophilic group such as ahydroxy group or carboxy group.

Specific examples of the acid-labile group include a group representedby the formula (1):

wherein R^(a1), R^(a2) and R^(a3) independently each represent a C1-C8alkyl group or a C3-C20 alicyclic hydrocarbon group, and R^(a1) andR^(a2) may be bonded each other to form a C2-C20 divalent hydrocarbongroup, and * represents a binding position,and a group represented by the formula (2)

wherein R^(a1′) and R^(a2′) independently each represent a hydrogen atomor a C1-C12 monovalent hydrocarbon group, and R^(a3′) represents aC1-C20 monovalent hydrocarbon group, or R^(a3′) binds to R^(a2′)together with —CO— attaching to R^(a2′) and R^(a3′) to form C3-C20 ringin which a methylene group of the divalent hydrocarbon group can bereplaced by —O— or —S—.

Specific examples of the C1-C8 alkyl group include a methyl group, anethyl group, a propyl group, an isopropyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group and an octyl group.

The alicyclic hydrocarbon group may be monocyclic or polycyclic.Examples of the alicyclic hydrocarbon group include a monocyclicalicyclic hydrocarbon group such as a C3-C20 cycloalkyl group (e.g. acyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, adimethylcyclohexyl group, a cycloheptyl group and a cyclooctyl group)and a polycyclic alicyclic hydrocarbon group such as a decahydronaphthylgroup, an adamantyl group, a norbornyl group, a methylnorbornyl group,and the following.

The alicyclic hydrocarbon group preferably has 5 to 16 carbon atoms.

When R^(a1) and R^(a2) of formula (1) are bonded each other to form aC2-C20 divalent hydrocarbon group, the moiety represented by —C(R^(a1))(R^(a2)) (R^(a3)) includes the following groups and the ring preferablyhas 3 to 12 carbon atoms:

wherein R^(a3) is the same as defined above and * represents a bindingposition to —O— of formula (1).

The group represented by the formula (1) wherein R^(a1), R^(a2) andR^(a3) independently each represent a C1-C8 alkyl group, preferably atert-butyl group, such as 1,1′-dialkylalkoxylcarbonyl group,

the group represented by the formula (1) wherein R^(a1) and R^(a2) arebonded each other to form an adamantyl ring and R^(a1) is a C1-C8 alkylgroup such as a 2-alkyladaman-2-tyloxycarbonyl group, and

the group represented by the formula (1) wherein R^(a1) and R^(a2) areC1-C8 alkyl groups and R^(a1) is an adamantin-1-yl group such as a1-(1-adaman-1-yl)-1-alkylalkoxycarbonyl group are preferable.

As to formula (2), examples of the hydrocarbon group include an alkylgroup, an alicyclic hydrocarbon group and an aromatic hydrocarbon group.

Examples of the alkyl group and the alicyclic hydrocarbon group includethe same as described above. Examples of the aromatic hydrocarbon groupinclude an aryl group such as a phenyl group, a naphthyl group, ap-methylphenyl group, a p-tert-butylphenyl group, a p-adamantylphenylgroup, a tolyl group, a xylyl group, a cumyl group, a mesityl group, abiphenyl group, an anthryl group, a phenanthryl group, a2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group.

It is preferred that at least one of R^(a1′) and R^(2′) is a hydrogenatom.

Examples of the group represented by formula (2) include the following.

The monomer having an acid-labile group, preferably one represented byformula (1) and/or formula (2) is preferably a monomer having anacid-labile group and carbon-carbon double bond, more preferably a(meth)acryalte compound having an acid-labile group.

Such (meth)acryalte compound preferably has a C5-C20 alicyclichydrocarbon group. Since the resin produced from (meth)acryalte compoundhaving C5-C20 alicyclic hydrocarbon group has a bulky structure, thephotoresist composition comprising the resin can show more excellentresolution.

Preferable resin (A) has a structural unit represented by the formula(a1-1) or (a1-2);

wherein R^(a4) and R^(a5) each independently represents a hydrogen atomor a methyl group, R^(a6) and R^(a7) each independently represents aC1-C10 aliphatic hydrocarbon group, L^(a1) and L^(a2) each independentlyrepresents *-O— or *-O— (CH₂)_(k1)—CO—O— in which * represents a bindingposition to —CO—, and k1 represents an integer of 1 to 7, m¹ representsan integer of 0 to 14, n1 represents an integer of 0 to 14, preferablyan integer of 0 to 10, and n1′ represents an integer of 0 to 3.

Examples of the aliphatic hydrocarbon group include a C1-C10 alkyl groupsuch as a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, a tert-butyl group, 2,2-dimethylethyl group,1-methylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group,1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group,1-propylbutyl group, a pentyl group, 1-methylpentyl group, a hexylgroup, 1,4-dimethylhexyl group, a heptyl group, 1-methylheptyl group andan octyl group; and the saturated cyclic hydrocarbon group such as acyclohexyl group, a methylcyclohexyl group, a dimethylcyolohexyl group,a cycloheptyl group, a methylcycloheptyl group, a norbornyl group and amethylnorbornyl group.

The alkyl group has preferably 1 to 8 carbon atoms, more preferably 1 to6 carbon atoms, and the saturated cyclic hydrocarbon group preferablyhas 3 to 10 carbon atoms and more preferably 3 to 6 carbon atoms.

L^(a1) and L^(a2) are preferably *-O— or *-O—(CH₂)_(f1)—CO—O— in which *represents a binding position to —CO—, and f1 represents an integer of 1to 4, and is more preferably *-O— or *-O—CH₂—CO—O—, and is especiallypreferably *-O—.

In the formula (a1-1), m1 is preferably an integer of 0 to 3, and ismore preferably 0 or 1. In the formula (a1-2), n1 is preferably aninteger of 0 to 3, and is more preferably 0 or 1. The n1′ is preferably0 or 1.

R^(a4) and R^(a5) are preferably methyl groups.

The compound from which the structural unit represented by (a1-1) isderived includes the compounds mentioned in JP2010-204646

As the structural unit represented by the formula (a1-1), preferred arestructural units represented by formulae (a1-1-1), (a1-1-2), (a1-1-3),(a1-1-4), (a1-1-5), (a1-1-6), (a1-1-7) and (a1-1-8), more preferred arestructural units represented by formulae (a1-1-1), (a1-1-2), (a1-1-3)and (a1-1-4).

As the structural unit represented by the formula (a1-2), preferred arethose represented by formulae (a1-2-1), (a1-2-2), (a1-2-3), (a1-2-4),(a1-2-5), (a1-2-6), (a1-2-7), (a1-2-8), (a1-2-9), (a1-2-10), (a1-2-11)and (a1-2-12), more preferred are those represented by formulae(a1-2-1), (a1-2-2), (a1-2-3), (a1-2-4), (a1-2-9) and (a1-2-10), andstill more preferred are those represented by formulae (a1-2-3) and(a1-2-9), and particularly more preferred are those represented byformula (a1-2-3).

examples of the monomer from which the structural units represented bythe formula (a1-2) are derived include1-ethyl-cyclopentant-1-yl(meth)acrylate,1-ethyl-cyclohexan-1-yl(meth)acrylate,1-ethyl-cyclohept-1-yl(meth)acrylate,1-methyl-cyclopent-1-yl(meth)acrylate, and1-isopropyl-cyclopent-1-yl(meth)acrylate.

The content of the structural unit represented by the formula (a1-1)and/or the formula (a1-2) in the resin (A) is preferably 10 to 95% bymole, more preferably 15 to 90% by mole, still more preferably 20 to 85%by mole, particularly more preferably 20 to 60% by mole based on 100% bymole of all the structural units of the resin (A).

When the resin (A) has an adamantane ring-containing structural unit,preferably the structural unit represented by formula (a1-1), thecontent of the adamantane ring-containing structural unit is preferably15% or more by mole based on 100% by mole of all of the structural unitrepresented by formula (a1). When the resin (A) has an adamantanering-containing structural unit in such amount as mentioned above, thephotoresist pattern obtained from the photoresist composition comprisingthe resin (A) can have more improved resistance to dry-etching. Thecontent of the structural unit represented by the formula (a1-1) and/orthe formula (a1-2) can be controlled by adjusting the amount of thecompounds from which the structural unit represented by the formula(a1-1) and/or the formula (a1-2) is derived at production of the resin(A). The resin (A) has more preferably the structural unit representedby formula (a1-1), of those represented by formulae (a1-1) and (a1-2).

Other structural units having an acid-labile group include a structuralunit derived from the monomer represented by formula (a1-3).

The resin which has the structural unit derived from the monomerrepresented by formula (a1-3) has a norbornene ring, which is a rigidstructure, at its main chain, so that the photoresist compositioncomprising such resin can provide a resist pattern excellent inresistance to dry-etching.

wherein R^(a9) represents a hydrogen atom; a C1-C3 aliphatic hydrocarbongroup which can have a substituent, e.g. a hydroxy group; a carboxylgroup; a cyano group; or —COOR^(a13) where R^(a13) represents a C1-C8aliphatic hydrocarbon group which can have a hydroxy group and in whicha methylene group can be replaced by —O— or —CO—, R^(a10), R^(a11) andR^(a12) each independently represent a C1-C12 aliphatic hydrocarbongroup which can have a hydroxy group and in which a methylene group canbe replaced by —O— or —CO—, and R^(a10) and R^(a11) can be bonded eachother to form a C3-C20 ring together with the carbon atom to whichR^(a11)) and R^(a11) are bonded.

Examples of the C1-C3 aliphatic hydrocarbon group which can have asubstituent include a methyl group, an ethyl group, a propyl group, ahydroxymethyl group and a 2-hydroxyethyl group. Examples of R^(a13)include a methyl group, an ethyl group, a propyl group, a2-oxo-oxolan-3-yl group and a 2-oxo-oxolan-4-yl group. Examples ofR^(a10), R^(a11) and R¹² include a methyl group, an ethyl group, acyclohexyl group, a methylcyclohexyl group, a hydroxycyclohexyl group,an oxocyclohexyl group and an adamantyl group, and examples of theC3-C20 ring formed by bonding R^(a10) and R^(a11) each other togetherwith the carbon atom to which R^(a10) and R^(a11) are bonded include acyclohexane ring and an adamantane ring.

Examples of the monomer represented by the formula (a1-3) include onementioned in JP2010-204646, such as tert-butyl5-norbornene-2-carboxylate, 1-cyclohexyl-1-methylethyl5-norbornene-2-carboxylate, 1-methylcyclohexyl5-norbornene-2-carboxylate, 2-methyl-2-adamantyl5-norbornene-2-carboxylate, 2-ethyl-2-adamantyl5-norbornene-2-carboxylate, 1-(4-methylcyclohexyl)-1-methylethyl5-norbornene-2-carboxylate, 1-(4-hydroxylcyclohexyl)-1-methylethyl5-norbornene-2-carboxylate, 1-methyl-1-(4-oxocyclohexyl)ethyl5-norbornene-2-carboxylate and 1-(1-adamantyl)-1-methylethyl5-norbornene-2-carboxylate.

As the monomer represented by the formula (a1-3), preferred are thoserepresented by formulae (a1-3-1), (a1-3-2), (a1-3-3) and (a1-3-4), morepreferred are those represented by formulae (a1-3-2), and (a1-3-4), andstill more preferred are those represented by formula (a1-3-2).

When the resin contains the structural unit derived from the monomerrepresented by the formula (a1-3), the content of the structural unitderived from the monomer represented by the formula (a1-3) is usually 10to 95% by mole and preferably 15 to 90% by mole and more preferably 20to 85% by mole based on total molar of all the structural units of theresin.

Other examples of the compound having an acid-labile group include amonomer represented by the formula (a1-4):

wherein R¹⁰ represents a hydrogen atom, a halogen atom, a C1-C6 alkylgroup or a C1-C6 halogenated alkyl group, R¹¹ is independently in eachoccurrence a halogen atom, a hydroxy group, a C1-C6 alkyl group, a C1-C6alkoxy group, a C2-C4 acyl group, a C2-C4 acyloxy group, an acryloylgroup or a methacryloyl group, l^(a) represents an integer of 0 to 4,R¹² and R¹³ each independently represent a hydrogen atom or a C1-C12hydrocarbon group, X^(a2) represents a single bond or a C1-C17 aliphatichydrocarbon group which can have a substituent and in which a methylenegroup can be replaced by —O—, —CO—, —S—, —SO₂ ⁻ or —N(R^(c))— whereinR^(c) represents a hydrogen atom or a C1-C6 alkyl group, and Y^(a3)represents C1-C18 hydrocarbon group which can have a substituent.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the C1-C6 alkyl group include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, an isobutylgroup, a sec-butyl group, a tert-butyl group, a pentyl group and a hexylgroup, and a C1-C4 alkyl group is preferable and a C1-C2 alkyl group ismore preferable and a methyl group is especially preferable.

Examples of the C1-C6 halogenated alkyl group include, preferablyfluorine-containing alkyl groups, such as a trifluoromethyl group, apentafluoroethyl group, a heptafluoropropyl croup, aheptafluoroisopropyl group, a nonafluorobutyl group, anonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group, a perfluorohexyl group, a perchloromethyl group,a perbromomethyl group and a periodomethyl group.

Examples of the C1-C6 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, an isopropoxy group, a butoxy group, anisobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxygroup and a hexyloxy group, and a C1-C4 alkoxy group is preferable and aC1-C2 alkoxy group is more preferable and a methoxy group is especiallypreferable.

Examples of the C2-C4 acyl group include an acetyl group, a propionylgroup and a butyryl group, and examples of the C2-C4 acyloxy groupinclude an acetyloxy group, a propionyloxy group and a butyryloxy group.

Examples of the C1-C12 hydrocarbon group include a C1-C12 aliphatichydrocarbon group such as a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, an isobutyl group, a sec-butylgroup, a tert-butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a 2-ethylhexyl group, a nonyl group, a decylgroup, an undecyl group and a dodecyl group, a C3-C12 alicyclichydrocarbon group such as a cyclohexyl group, an adamantyl group, a2-alkyl-2-adamantyl group, a 1-(1-adamantyl)-1-alkyl group and anisobornyl group, an C6-C12 aromatic hydrocarbon group and a group formedby combining one or more above-mentioned groups. Among them, preferredare an isopropyl group, a butyl group, a sec-butyl group, a tart-butylgroup, a pentyl group, a hexyl group, an octyl group, a 2-ethylhexylgroup, a cyclohexyl group, an adamantyl group, a 2-alkyl-2-adamantylgroup, a 1-(1-adamantyl)-1-alkyl group and an isobornyl group.

Examples of the C1-C17 divalent saturated hydrocarbon group include aC1-C17 alkanediyl group such as a methylene group, an ethylene group, apropane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a heptane-1,7-diyl group, anoctane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diylgroup, a undecane-1,11-diyl group, a dodecane-1,12-diyl group, atridecane-1,13-diyl group, a tetradecane-1,14-diyl group, apentadecane-1,15-diyl group, a hexadecane-1,16-diyl group and aheptadecane-1,17-diyl group.

Examples of the C1-C12 aliphatic hydrocarbon group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, an isobutyl group, a sec-butyl group, a tert-butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group and adodecyl group. Examples of the C3-C18 saturated cyclic hydrocarbon groupinclude a, cyclopropyl group, a cyclobutyl group, a cyclopentyl group, acyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononylgroup, a cyclodecyl group, a norbornyl group, a 1-adamantyl group, a2-adamantyl group, an isobornyl group and the following groups:

Examples of the C6-C18 aromatic hydrocarbon group include a phenylgroup, a naphthyl group, an anthryl group, a p-methylphenyl group, ap-tert-butylphenyl group and a p-adamantylphenyl group.

The substituents in X^(a2) and Y^(a3) include a halogen atom, a hydroxygroup, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C4 acyl group anda C2-C4 acyloxy group. Preferred substituents in X^(a2) and Y^(a3) are ahydroxy group.

The monomer represented by the formula (a1-4) includes those mentionedin JP2010-204646, preferred are the monomers represented by the formulae(a1-4-1), (a1-4-2), (a1-4-3), (a1-4-4), (a1-4-5), (a1-4-6) and (a1-4-7)and more preferred are the monomers represented lay the formulae(a1-4-1), (a1-4-2), (a1-4-3), (a1-4-4) and (a1-4-5).

When the resin contains the structural unit derived from the monomerrepresented by the formula (a1-4), the content of the structural unitderived from the monomer represented by the formula (a1-4) is usually 10to 95% by mole and preferably 15 to 90% by mole and more preferably 20to 85% by mole based on total molar of all the structural units of theresin.

Other examples of the compound having an acid-labile group include amonomer represented by the formula (a1-5);

wherein R³¹ represents a hydrogen atom, a halogen atom, a C1-C6 alkylgroup which can have a halogen atom, L⁵ represents —O—, —S—or*-O—(CH₂)_(k4)—CO—O—, k4 represents an integer of 1 to 7, *representsa binding position to —CO—, L³ and L⁴ independently each represent —O—,—S—, or —O—(CH₂)_(k5)—CO—O—, k5 represents an integer of 1 to 7, Z^(1′)represents a single bond or a C1-C6 alkylene group in which a methylenegroup can be replaced by —O— or —CO—, s¹ and s^(1′) independently eachrepresent an integer of 0 to 4.

R³¹ is preferably a hydrogen atom, a methyl group, or trifluoromethylgroup.

L⁵ is preferably —O—.

It is preferred that one of L³ and L⁴ is —O— and the other is —S—.

In the formula (a1-5), s¹ is preferably l and s^(1′) is preferably 0, 1or 2.

Z¹ is preferably a single bond or —CH₂—CO—O—.

Examples of the monomer represented by the formula (a1-5) include thefollowing.

When the resin contains the structural unit derived from the monomerrepresented by the formula (a1-5), the content of the structural unitderived from the monomer represented by the formula (a1-5) is preferably1 to 95% by mole and more preferably 3 to 90% by mole and still morepreferably 5 to 85% by mole based on total molar of all the structuralunits of the resin.

The resin (A) may further comprise a structural unit having noacid-labile group. The resin (A) may further comprise one or more kindsof structural units having no acid-labile group. The content of thestructural unit having an acid-labile group is preferably 10 to 80% bymole, more preferably 20 to 60% by mole of the total mole amount of allof structural units in the resin (A).

In case where the resin (A) comprises a structural unit having noacid-labile group, the molar ratio of the structural unit having anacid-labile group to the structural unit having no acid-labile group ispreferably (10 to 80)/(90 to 20), more preferably (20 to 60)/(80 to 40)[=(the structural unit having an acid-labile group/the structural unithaving no acid-labile group)]. When the resin (A) has the structuralunits in such amount as mentioned above, the photoresist patternobtained from the photoresist composition comprising the resin (A) canhave more improved resistance to dry-etching.

The structural unit having no acid-labile group preferably has a hydroxygroup or a lactone ring.

When the resin (A) has a structural unit having no acid-labile group buthaving a hydroxy group or a lactone ring, the photoresist compositioncomprising such resin can show adhesiveness of photoresist to asubstrate and provide a photoresist pattern with good resolution.

The resin (A) may comprise one or more kinds of structural units havingno acid-labile group but having a hydroxy group.

The structural unit having no acid-labile group in the resin (A) can besuitably selected depending on exposure source for producing photoresistpattern from the photoresist composition having comprising the resin(A).

When KrF excimer laser (wavelength: 248 nm) lithography system, or ahigh energy laser such as electron beam and extreme ultraviolet is usedas an exposure system, preferred is a resin which has the structuralunit having no acid-labile group but having a phenolic-hydroxy group.When ArF excimer laser (wavelength: 193 nm) is used as an exposuresystem, preferred is a resin which has the structural unit representedby the formula (a2-1).

The structural unit having no acid-labile group but having a hydroxygroup, preferably has a hydroxyadamantyl group.

Preferred examples of the structural unit having no acid-labile groupbut having a hydroxy group include a structural unit represented by theformula (a2-1):

wherein R^(a14) represents a hydrogen atom or a methyl group, R^(a15)and R^(a16) each independently represent a hydrogen atom, a methyl groupor a hydroxy group, L^(a) represents *—O— or *-O—(CH₂)_(k2)—CO—O— inwhich * represents a binding position to —CO—, and k2 represents aninteger of 1 to 7, and of represents an integer of 0 to 10.

In the formula (a2-1), L^(a3) is preferably *-O— or *-O—(CH₂)_(f2)—CO—O—in which * represents a binding position to —CO—, and f2 represents aninteger of 1 to 4, is more preferably *-O— and *-O—CH₂—CO—O—, and isstill more preferably *-O—.

R^(a14) is preferably a methyl group. R^(a15) is preferably a hydrogenatom. R^(a16) is preferably a hydrogen atom or a hydroxy group. ol ispreferably 0, 1, 2 or 3 and is more preferably 0 or 1.

The structural unit represented by the formula (a2-1) includes thoserepresented by the formula as follow:

The structural unit represented by formula (a2-1) includes those derivedfrom the compounds mentioned in JP2010-204646A.

Among them, preferred are the structural units represented by formulae(a2-1-1), (a2-1-2), (a2-1-3) and (a2-1-4), more preferred are thestructural units represented by formulae (a2-1-1) and (a2-1-3).

when the resin has the structural unit represented by the formula(a2-1), the content of the structural unit represented by the formula(a2-1) is usually 3 to 45% by mole, and preferably 5 to 40% by mole, andmore preferably 5 to 35% by mole, based, on total molar of all thestructural units of the resin.

Examples of the structural unit having no acid-labile group and having aphenolic hydroxy group include one represented by the formula (a2-0):

wherein R^(a30) represents a hydrogen atom, a halogen atom, a C1-C6alkyl group or a C1-C6 halogenated alkyl group, R^(a31) is independentlyin each occurrence a halogen atom, a hydroxy group, a C1-C6 alkyl group,a C1-C6 alkoxy group, a C2-C4 acyl group, a C2-C4 acyloxy group, anacryloyl group or a Methacryloyl group, ma represents an integer of 0 to4.

In the formula (a2-0), examples of the halogen atom include a fluorineatom, examples of the C1-C6 alkyl group include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, an isobutylgroup, a sec-butyl group, a tert-butyl group, a pentyl group and a hexylgroup. Examples of the C1-C6 halogenated alkyl group include atrifluoromethyl group, a pentafluoroethyl group, a heptafluoropropylgroup, a heptafluoroisopropyl group, a nonafluorobutyl group, anonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group and a perfluorohexyl group. R^(a30)) representspreferably a C1-C4 alkyl group, more preferably a C1-C2 alkyl group, andstill more preferably a methyl group.

Examples of the C1-C6 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, an isopropoxy group, a butoxy group, anisobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxygroup and a hexyloxy group. Examples of the C2-C4 acyl group include anacetyl group, a propionyl group and a butyryl group, and examples of theC2-C4 acyloxy group include an acetyloxy group, a propionyloxy group anda butyryloxy group. R^(a31) represents preferably a C1-C4 alkoxy group,more preferably a C1-C2 alkoxy group, and still more preferably amethoxy group.

In the formula (a2-0), ma is preferably 0, 1 or 2, and is morepreferably 0 or 1, and especially preferably 0.

The structural unit represented by the formula (a2-0) is preferablyrepresented by the formulae (a2-0-1) (a2-0-1), (a2-0-3) and (a2-0-4).Monomers from which such unit is derived include compounds mentioned inJP2010-204634A.

The resin having the structural unit represented by the formula (a2-0)can be produced, for example, by polymerizing a compound in which ahydroxy group has been protected with a protecting group such as anacetyl group and from which the structural unit represented by theformula (a2-0) is derived, followed by conducting deprotection of theobtained polymer with an acid or a base.

The resin having the structural unit represented by the formula (a2-0)can be produced from a hydroxylstylene as a monomer. Among them,preferred are 4-hydroxystyrene and 4-hydroxy-α-methylstyrene.

When such resin is produced from a hydroxylstylene, it can be producedby protecting a phenolic hydroxy group with an acetyl group to produceacetylhydroxylstylene, polymerizing acetylhydroxylstylene to obtain aresin having the structural unit represented by the formula (a2),followed by deprotecting acetylhydroxy groups of the resin to obtain aresin having the structural unit represented by the formula (a2-0). Thedeprotection of acetylhydroxy groups requires not remarkably detractingfrom other structural units such as the unit (a1).

When the resin (A) has the structural unit represented by the formula(a2-0), the content of the structural unit represented by the formula(a2-0) is usually 10 to 90% by mole and preferably 10 to 85% by mole andmore preferably 15 to 80% by mole based on total molar of all thestructural units of the resin.

As to the structural unit having no acid-labile group but having alactone ring, examples of the lactone ring include a monocyclic lactonering such as β-propiolactone ring, γ-butyrolactone ring andδ-valerolactone ring, and a condensed ring formed from a monocycliclactone ring and the other ring. Among them, preferred areγ-butyrolactone ring and a condensed lactone ring formed fromγ-butyrolactone ring and the other ring.

Preferable examples of the structural unit having no acid-labile groupbut having a lactone ring include those represented by the formulae(a3-1), (a3-2) and (a3-3):

wherein L^(a4), L^(a5) and L^(a6) each independently represent *-O— or*-O—(CH₂)_(k3)—CO—O— in which * represents a binding position to —CO—and k3 represents an integer of 1 to 7, R^(a18), R^(a19) and R^(a20)each independently represent a hydrogen atom or a methyl group, R^(a21)represents a C1-C4 aliphatic hydrocarbon group, R^(a22) and R^(a23) areindependently in each occurrence a carboxyl group, a cyano group or aC1-C4 aliphatic hydrocarbon group, and p1 represents an integer of 0 to5, q1 and r1 independently each represent an integer of 0 to 3.

It is preferred that L^(a4), L^(a5) and L^(a6) each independentlyrepresent *-O— or *-O—(CH₂)_(d1)—CO—O— in which * represents a bindingposition to —CO— and d1 represents an integer of 1 to 4, and it is morepreferred that L^(a4), L^(5a) and L^(a6) are *-O— and *-O—CH₂—CO—O—, andit is still more preferred that L^(a4), L^(a5) and L^(a6) are *-O—.

R^(a18), R^(a19) and R^(a20) are preferably methyl groups. R^(a21) ispreferably a hydrogen atom. It is preferred that R^(a22) and R^(a23) areindependently in each occurrence a carboxyl group, a cyano group or amethyl group. It is preferred that p1 is an integer of 0 to 2, and it ismore preferred that p1 is 0 or 1. It is preferred that q1 and r1independently each represent an integer of 0 to 2, and it is morepreferred that q1 and r1 independently each represent 0 or 1.

Preferred examples of the structural unit represented by the formula(a3-1) include those represented by the formula (a3-1-1), the formula(a3-1-2), the formula (a3-1-3) or the formula (a3-1-4).

Examples of the structural unit represented by the formula (a3-2)include preferably those represented by the formula (a3-2-1), theformula (a3-2-2), the formula (a3-2-3) or the formula (a3-2-4).

Preferred examples of the structural unit represented by the formula(a3-3) include those represented by the formula (a3-3-1), the formula(a3-3-2), the formula (a3-3-3) or the formula (a3-3-4).

Preferred structural unit having no acid-labile group but having alactone ring are those represented by the formulae (a3-1-1), (a3-2-2),(a3-2-3) and (a3-2-4), and more preferred are those represented by theformulae (a3-1-1) and (a3-2-3).

The structural units represented by the formula (a3-1), formula (a3-2)and formula (a3-3) can be derived from the counterpart monomersmentioned in JP2010-204646A.

The content of the structural unit having no acid-labile group buthaving a lactone ring is usually 5 to 70% by mole, preferably 10 to 65%by mole, still more preferably 10 to 60% by mole based on the totalmolar of all structural units of the resin (A).

When the resin contains the structural unit represented by the formula(a3-1), formula (a3-2) or formula (a3-3), the content thereof ispreferably 5 to 60% by mole, more preferably 5 to 50% by mole and stillmore preferably 10 to 50% by mole, based on total molar of all thestructural units of the resin.

The resin may further contain another structural unit having noacid-labile group, besides the structural unit represented by formula(a2) or formula (a3).

The resin may further contain a structural unit derived from a monomerrepresented by the formula (a4-1), besides the structural unitrepresented by formula (a2) or formula (a3), as the structural unithaving no acid-labile group.

wherein R^(a41) represents a C1-C12 monovalent aliphatic hydrocarbongroup in which a methylene group can be replaced by an oxygen atom or acarbonyl group, or a C6-C12 monovalent aromatic hydrocarbon group;

-   A^(a41) represents a C1-C6 alkanediyl group which can have a    substituent, or a group represented by formula (a-g1)    -A^(a42)    X^(a41)-A^(a43)    _(s)X^(a42)-A^(a44)-  (a-g1)    where s represents 0 or 1, A^(a42) and A^(a44) each independently    represent a single bond or a C1-C5 aliphatic hydrocarbon group which    can have a substituent, X^(a41) and X^(a42) are independently in    each occurrence an oxygen atom, a carbonyl group, a carboxyl group,    or an oxycarbonyl group, provided that the carbon atoms of A^(a42),    A^(a43), A^(a44), X^(a41) and X^(a42) amount to 6 or less in total;    and-   R^(a42) represents an aliphatic hydrocarbon group which can have a    substituent.

In the aliphatic hydrocarbon group represented by R^(a42), any ofmethylene groups can be replaced by a carbon-carbon double bond, howeverthe aliphatic hydrocarbon group has preferably no carbon-carbon doublebond.

The aliphatic hydrocarbon group includes a straight or cyclic alkylgroup, alicyclic group, and a group comprising the alkyl group andalicyclic group.

In the aliphatic hydrocarbon group represented by R^(a42), examples ofthe C1-C12 alkyl group include a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, a pentyl group, a hexyl group,a heptyl group, an octyl group, a decyl group, and a dodecyl group.

The aromatic hydrocarbon group includes a phenyl group, a naphthylgroup, an anthryl group, biphenyl group, phenanthryl group, fluorenylgroup.

The aliphatic hydrocarbon group represented by R⁴² preferably has asubstituent. The substituent for the aliphatic hydrocarbon group ispreferably a fluorine atom or a group represented by formula (a-g3)-X^(a43)-A^(a45)  (a-g3)

-   in which X^(a43) represents an oxygen atom, a carbonyl group, a    carboxyl group, or an oxycarbonyl group, and-   A^(a45) represents a C3-C17 aliphatic hydrocarbon group which can    have a fluorine atom.-   R^(a42) preferably represents a group represented by formula (a-g2)    -A^(a46)-X^(a44)-A^(a47)  (a-g2)    in which A^(a46) represents a C3-C17 aliphatic hydrocarbon group    which can have a halogen atom, and-   X^(a44) represents a carboxyl group, or an oxycarbonyl group, and-   A^(a47) represents a C3-C17 aliphatic hydrocarbon group which can    have a halogen atom, provided that the carbon atoms of A^(a46),    A^(a47) and-   X^(a44) amount to 18 or less in total.

The aliphatic hydrocarbon group includes a straight or cyclic alkylgroup having a halogen atom, an alicyclic hydrocarbon group having ahalogen atom, a cycloalkyl group having a halogen atom.

Here, the “alkyl group having a halogen atom” means an alkyl group inwhich any or all of hydrogen atoms have been replaced by a halogen atom,and the “cycloalkyl group having a halogen atom” means a cycloalkylgroup in which any or all of hydrogen atoms have been replaced by ahalogen atom,

The halogen atom includes fluorine atom, chlorine atom, bromine atom, oriodorine atom, preferably fluorine atom.

The monomer represented by the formula (a4-1) wherein R^(a42) representsan ethylene group includes the one represented by formulae (a4-1-1),(a4-1-2), (a4-1-3), (a4-1-4), (a4-1-5), (a4-1-6), (a4-1-7), (a4-1-8),(a4-1-9), (a4-1-10), (a4-1-11), (a4-1-12), (a4-1-13), (a4-1-14),(a4-1-15), (a4-1-16), (a4-1-17), (a4-1-18), (a4-1-19), (a4-1-20),(a4-1-21) and (a4-1-22).

The monomer represented by the formula (a4-1) wherein R^(a42) representsan aliphatic hydrocarbon group having a fluorine atom is preferably aperfluoroalkyl group in which all of hydrogen atoms have been replacedby fluorine atoms or a perfluorocycloalkyl group in which all ofhydrogen atoms have been replaced by fluorine atoms.

Examples of the monomer represented by the formula (a4-1) whereinR^(a42) represents a perfluoroalkyl group or a perfluorocycloalkyl groupinclude that represented by formulae (a4-1-3), (a4-1-4), (a4-1-7),(a4-1-8), (a4-1-11), (a4-1-12), (a4-1-15), (a4-1-16), (a4-1-19),(a4-1-20), (a4-1-21) and (a4-1-22). R^(a42) represents preferably aperfluoroalkyl group such as C1-C8 perfluoroalkyl group including aperfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group,a perfluoroheptyl group, a perfluorooctyl group, more preferably C1-C6perfluoroalkyl group, and still more preferably C1-C3 perfluoroalkylgroup.

The aliphatic hydrocarbon group represented by R^(a42) can have one ormore groups represented by formula (a-g3). The aliphatic hydrocarbongroup has preferably 15 or less, more preferably 12 or less, carbonatoms in total. Considering such total of carbon atoms, the aliphatichydrocarbon group represented by R^(a42) has preferably one grouprepresented by formula (a-g3).

The monomer represented by formula (a4-1) in which R^(a42) is analiphatic hydrocarbon group having one group represented by formula(a-g2) is specifically represented by the formula (a4-1′).

where R^(a41), A^(a41), A^(a46), X^(a44) and A^(a47) are as definedabove.

In the formula (a4-1′), A^(a46) or A^(a47) is preferably an aliphatichydrocarbon group having a halogen atom. More preferred is that A^(a46)is an aliphatic hydrocarbon group having a halogen atom, still morepreferred is that A^(a46) is an alkanediyl group having a fluorine atom,partioularly more preferred is that A^(a46) is a perfluoroalkanediylgroup in which all of hydrogen atoms have been replaced by fluorineatoms.

The monomer represented by the formula (a4-1′) wherein R^(a41)represents an ethylene group and R^(a42) represents anperfluoroalkanediyl group includes the one represented by formulae(a4-1′-1), (a4-1′-2), (a4-1′-3), (a4-1′-4), (a4-1′-5), (a4-1′-6),(a4-1′-7), (a4-1′-8), (a4-1′-9), (a4-1′-10), (a4-1′-11), (a4-1′-12),(a4-1′-13), (a4-1′-14), (a4-1′-15), (a4-1′-16), (a4-1′-17), (a4-1″-18),(a4-1′-19), (a4-1′-20), (a4-1′-21) and (a4-1′-22).

The aliphatic hydrocarbon group represented by A^(a46) or A^(a47) canhave 17 or less carbon atoms, if the total of the carbon atoms whichA^(a46) and A^(a47) have are 17 or less. A^(a46) has preferably 1 to 6,more preferably 1 to 3, carbon atoms. A^(a47) has preferably 4 to 15,more preferably 5 to 12, carbon atoms.

A^(a47) is preferably a C6-C12 alicyclic hydrocarbon group, morepreferably a cyclohexyl group or an adamantyl group.

When the moiety *-A^(a46)-X^(a44)-A^(a47), where * represents a bindingposition to a carbonyl group, is represented by the following formulae,the combination of A^(a46) and A^(a47) is preferred.

The compounds represented by formulae (a4-1′-9), (a4-1′-10), (a4-1′-11),(a4-1′-12), (a4-1′-13), (a4-1′-14), (a4-1′-15), (a4-1′-16), (a4-1′-17),(a4-1′-18), (a4-1′-19) and (a4-1′-20) have these preferred combinationof A^(a46) and A^(a47).

When the resin contains the structural unit derived from the monomerrepresented by the formula (a4-1), the content of the structural unitderived from the monomer represented by the formula (a4-1) is usually 1to 20% by mole, preferably 2 to 15% by mole and more preferably 3 to 10%by mole based on total molar of all the structural units of the resin.

The resin (A) may comprise any other structural units than one derivedfrom the monomer represented by formula (a1), (a2), (a3) or (a4)

The resin (A) is generally a polymer of the compound from which thestructural unit having an acid labile group is derived, preferably acopolymer of the compound from which the structural unit having an acidlabile group is derived and the compound from which the structural unithaving no acid labile group is derived, more preferably a copolymer ofthe compound from which the structural unit represented by formula(a1-1) and/or formula (a1-2) is derived, and the compound from which thestructural unit represented by formula (a2) and/or formula (a3) isderived.

The resin (A) preferably has a structural unit having an adamantyl groupsuch as one represented by formula (a1-1) as the structural unit havingan acid-labile group.

The resin (A) preferably has a structural unit having a hydroxyadamantyl group such as one represented by formula (a2-1) as thestructural unit having no acid-labile group.

The resin (A) has preferably at least one selected from a structuralunit having no acid-labile group but having γ-butyrolactone ring, suchas one represented by formula (a3-1), and a structural unit having noacid-labile group but having a condensed lactone ring formed fromγ-butyrolactone ring and a norbornane ring, such as one represented byformula (a3-2).

The resin (A) can be produced according to known polymerization methodssuch as radical polymerization.

The resin (A) usually has 2,500 or more of the weight-average molecularweight, preferably 3,000 or more of the weight-average molecular weight.The resin usually has 50,000 or less of the weight-average molecularweight, preferably has 30,000 or less of the weight-average molecularweight.

The weight-average molecular weight can be measured with gel permeationchromatography (standard: polyethylene).

The photoresist composition of the present invention may furthercomprise another resin than the resin having an acid-labile group. Thus,the photoresist composition may comprise the resin having an acid-labilegroup and the resin having no acid-labile group, preferably the resinhaving no acid-labile group but having the structural unit derived fromthe monomer represented by the formula (a4-1).

In the resin having no acid-labile group but having the structural unitderived from the monomer represented by the formula (a4-1), which resinis sometimes referred to as “resin (X)”, the content of the structuralunit derived from the monomer represented by the formula (a4-1) ispreferably 80% by mole or more, more preferably 85% by mole or more, andstill more preferably 90% by mole or more. The resin (X) maysubstantially consist of the structural unit derived from the monomerrepresented by the formula (a4-1). The resin (X) may comprise otherstructural units, such as the structural units represented by theformula (a2) or the formula (a3).

The resin (X) can be obtained usually by polymerizing the monomerrepresented by the formula (a4-1), as necessary with a monomer having noacid-labile group, such as a compound from which the structural unitsrepresented by the formula (a2) or the formula (a3) is derived, in aknown manner.

The resin (X) has usually 8,000 or more of the weight-average molecularweight, preferably 10,000 or more of the weight-average molecularweight. The resin usually has 80,000 or less of the weight-averagemolecular weight, preferably has 60,000 or less of the weight-averagemolecular weight.

The weight-average molecular weight can be measured with gel permeationchromatography (standard: polyethylene).

The photoresist compositions of the present invention can contain abasic compound as a quencher. The basic compound has the property thatit can trap an acid, especially an acid generated from the acidgenerator by applying a radiation.

The basic compound is preferably a basic nitrogen-containing organiccompound, and examples thereof include an amine compound and an ammoniumsalt. Amine compound includes an aliphatic amine and an aromatic amine.Examples of the aliphatic amine include a primary amine, a secondaryamine and a tertiary amine. Examples of the aromatic amine include anaromatic amine in which aromatic ring has one or more amino groups suchas aniline and a heteroaromatic amine such as pyridine.

The basic compounds include preferably a compound represented by theformulae (C1), (C2), (C3), (C4), (C5), (C6), (C7) and (C8), morepreferably a compound represented by the formulae (C1), still morepreferably a compound represented by the formulae (C1-1).

wherein R^(c1), R^(c2) and R^(c3) independently represent a hydrogenatom, a C1-C6 alkyl group, a C5-C10 alicyclic hydrocarbon group or aC6-C10 aromatic hydrocarbon group, and the alkyl group and the alicyclichydrocarbon group can have a substituent selected from the groupconsisting of a hydroxy group, an amino group and a C1-C6 alkoxy group,and the aromatic hydrocarbon group can have a substituent selected fromthe group consisting of C1-C6 alkyl groups, a C5-C10 alicyclichydrocarbon group, a hydroxy group, an amino group, and a C1-C6 alkoxygroup,

wherein R^(c2) and R^(c3) are defined as above, each of R^(c4)independently represents a C1-C6 alkyl group, a C1-C6 alkoxy group, aC5-C10 alicyclic hydrocarbon group or a C6-C10 aromatic hydrocarbongroup, and m3 represents an integer of 0 to 3,

wherein R^(c5), R^(c6), R^(c7) and R^(c8) are defined same as R^(c1),each of R^(c9) independently represents a C1-C6 alkyl group, a C3-C6alicyclic group, or a C2-C6 alkanoyl group, and n3 represents an integerof 0 to 8,

wherein each of R^(c10), R^(c11), R^(C12), R^(c13) and R^(c16) isdefined same as R^(c1), each of R^(C14), R^(c15) and R^(c17) is definedsame as R^(c4),

-   L^(c1) represents a C1-C6 alkanediyl group, —CO—, —C(—NH)—, —S— or a    combination thereof, and o3 and p3 respectively represent an integer    of 0 to 3,

wherein each of R^(c18), R^(c19) and R^(c20) is defined same as R^(C4),

-   L^(c2) represents a single band, a C1-C6 alkanediyl group, —CO—,    —C(═NH)—, —S— or a combination thereof, and q3, r3 and p3    respectively represent an integer of 0 to 3.

Examples of the compound represented by the formula (C1) include1-naphthylamine, 2-naphthylamine, aniline, diisopropylaniline,2-methylaniline, 3-methylaniline, 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylamine, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, triethylamine, trimethylamine, tripropylamine,tributylamine, tripentylamine, trihexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, methyldibutylamine,methyldipentylamine, methyldihexylamine, methyldicyclohexylamine,methyldiheptylamine, methyldioctylamine, methyldinonylamine,methyldidecylamine, ethyldibutylamine, ethydipentylamine,ethyldihexylamine, ethydiheptylamine, ethyldioctylamine,ethyldinonylamine, ethyldidecylamine, dicyclohexylmethylamine,tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine,ethylenediamine, tetramethylenediamine, hexamethylenediamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane and4,4′-diamino-3,3′-diethyldiphenylmethane. Among them, preferred isdiisopropylaniline and more preferred is 2,6-diisopropylaniline

Examples of the compound represented by the formula (C2) includepiperazine.

Examples of the compound represented by the formula (C3) includemorpholine.

Examples of the compound represented by the formula (C4) includepiperidine and hindered amine compounds having a piperidine skeleton asdisclosed in JP 11-52575 A1.

Examples of the compound represented by the formula (C5) include2,2′-methylenebisaniline.

Examples of the compound represented by the formula (C6) includeimidazole and 4-methylimidazole.

Examples of the compound represented by the formula (C7) includepyridine and 4-methylpyridine.

Examples of the compound represented by the formula (C8) includedi-2-pyridylketone, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,3-di(4-pyridyl)propane, 1,2-bis(2-pyridyl)ethene,1,2-bis(4-pyridyl)ethene, 1,2-di(4-pyridyloxy)ethane, 4,4′-dipyridylsulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine,2,2′-dipicolylamine and bipyridine.

Examples of the ammonium salt include tetramethylammonium hydroxide,tetrabutylammonium hydroxide, tetrahexylammonium hydroxide,tetraoctylammonium hydroxide, phenyltrimethylammonium hydroxide,(3-trifluoromethylphenyl)trimethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”).

The photoresist compositions of the present invention usually contain asolvent.

Examples of the solvent include a glycol ether ester such as ethylcellosolve acetate, methyl cellosolve acetate and propylene glycolmonomethyl ether acetate; an ester such as ethyl lactate, butyl acetate,amyl acetate and ethyl pyruvate; a ketone such as acetone, methylisobutyl ketone, 2-heptanone and cyclohexanone; and a cyclic ester suchas γ-butyrolactone.

The photoresist compositions of the present invention can contain, ifnecessary, a small amount of various additives such as a sensitizer, adissolution inhibitor, other polymers, a surfactant, a stabilizer and adye as long as the effect of the present invention is not prevented.

The photoresist compositions of the present invention can usually beprepared by mixing, in a solvent, an acid generator containing the SALT(I), and a resin (A), and if necessary a basic compound, the resin (X)and/or additives at a suitable ratio for the composition, optionallyfollowed by filtrating the mixture with a filter having 0.2 μm of a paresize.

The order of mixing these components is not limited to any specificorder. The temperature at mixing the components is usually 10 to 40° C.,which can be selected in view of the resin or the like.

The mixing time is usually 0.5 to 24 hours, which can be selected inview of the temperature. The means for mixing the components is notlimited to specific one. The components can be mixed by being stirred.

The amounts of the components in the photoresist compositions can beadjusted by selecting the amount to be used for production of them.

The total content of the acid generator is preferably 0.1 part by weightor more, more preferably 1 part by weight or more, still more preferably3 part by weight or more, and the content of SALT (I) is preferably 40parts by weight or less, and more preferably 35 parts by weight or less,per 100 parts by weight of the resin (A).

The content of SALT (I) is preferably 10 part by weight or more, morepreferably 30 part by weight or more, per 100 parts by weight of thetotal amount of the acid generators. The acid generator may consist ofSALT (I).

The photoresist composition of the present invention usually contains80% by weight or more of the resins based on sum of solid component. Thephotoresist composition of the present invention usually contains 99$ byweight or less of the resins based on sum of solid component. In thisspecification, “solid component” means components other than solvent inthe photoresist composition,

When the photoresist composition contains the resin (X), the content ofthe resin is usually 0.1 to 30 weight parts, preferably 0.5 to 20 weightparts, more preferably 1 to 15 weight parts relative to 100 weight partsof the resin (A).

When the photoresist compositions contain the basic compound, thecontent thereof is usually 0.01 to 5%, preferably 0.01 to 3%, morepreferably 0.01 to 1% by weight based on sum of solid component.

The amount of the solvent is usually 90% by weight or more, preferably92% by weight or more preferably 94% by weight or more based on totalamount of the photoresist composition of the present invention. Theamount of the solvent is usually 99.9% by weight or less and preferably99% by weight or less based on total amount of the photoresistcomposition of the present invention.

The photoresist compositions of the present invention are useful for achemically amplified photoresist composition.

A photoresist pattern can be produced using the photoresist compositionof the present invention by the following steps (1) to (5):

(1) a step of applying the photoresist composition of the presentinvention on a substrate,

(2) a step of forming a photoresist film by conducting drying,

(3) a step of exposing the photoresist film to radiation,

(4) a step of baking the exposed photoresist film, and

(5) a step of developing the baked photoresist film to form aphotoresist pattern.

The applying of the photoresist composition on a substrate is usuallyconducted using a conventional apparatus such as spin coater. Thephotoresist composition is preferably filtrated with filter having 0.2μm of a pore size before applying. Examples of the substrate include asilicon wafer or a quartz wafer on which a sensor, a circuit, atransistor or the like is formed. The substrate may be coated with areflect-preventing layer such as one containing hexamethyldisilazane.For forming the reflect-preventing layer, such composition for organicreflect-preventing layer as available on the market can be used.

The photoresist film is usually formed by heating the coat layer with aheating apparatus such as hot plate or a decompressor, to thereby dryoff the solvent. The heating temperature is preferably 50 to 200° C.,and the operation pressure is preferably 1 to 1.0*10⁵ Pa. Theseconditions can be selected in view of the solvent.

The photoresist film obtained is exposed to radiation using an exposuresystem. The exposure is usually conducted through a mask having apattern corresponding to the desired photoresist pattern. Examples ofthe exposure source include a light source radiating laser light in aUV-region such as a KrF excimer laser (wavelength: 248 nm), an ArFexcimer laser (wavelength: 193 nm) and a F2 laser (wavelength: 157 nm),and a light source radiating harmonic laser light in a far UV region ora vacuum UV region by wavelength conversion of laser light from a solidlaser light source (such as YAG or semiconductor laser). The exposuresource may be electric beam or extremely ultraviolet (EUV).

Exposure through a mask makes the composition layer have exposed areasand unexposed area. At the exposed area, the acid generator contained inthe component layer gives an acid due to exposure energy. The acidgenerated from the acid generator acts on an acid-labile group of theresin, so that the deproteetion reaction proceeds, resulting that theresin shows hydrophilic. Therefore, the resin becomes soluble with analkaline solution at exposed area of the composition layer. On the otherhand, unexposed area of the composition layer remains insoluble orpoorly soluble in an aqueous alkali solution even after exposure. Thesolubility for an aqueous alkali solution is much different between theexposed area and unexposed area.

The step of baking of the exposed photoresist film is so calledpost-exposure bake, which is conducted with heating means such as hotplates. The temperature of baking of the exposed photoresist film ispreferably 50 to 200′C, and more preferably 70 to 150′C. Thedeprotection reaction further proceeds by post-exposure bake.

The development of the baked photoresist film is usually carried outwith alkaline developer using a development apparatus. The developmentcan be conducted by contacting the baked photoresist film into with anaqueous alkaline solution to thereby remove the film at exposed areafrom the substrate while remain the film at unexposed area, forming thephotoresist pattern. The alkaline developer to be used may be any one ofvarious alkaline aqueous solution used in the art. Generally, an aqueoussolution of tetramethylammonium hydroxide or(2-hydroxyethyl)trimethylammonium hydroxide (commonly known as“choline”) is often used.

After development, the photoresist pattern formed is preferably washedwith ultrapure water, and the remained water on the photoresist patternand the substrate is preferably removed.

The photoresist composition of the present invention is suitable for ArFexcimer laser lithography, KrF excimer laser lithography, EUV exposurelithography and EB (electron beam) lithography.

EXAMPLES

The present invention will be described more specifically by Examples,which are not construed to limit the scope of the present invention.

The “%” and “part(s)” used to represent the content of any component andthe amount of any material used in the following examples andcomparative examples are on a weight basis unless otherwise specificallynoted.

The weight-average molecular weight of any material used in thefollowing examples is a value found by gel permeation chromatography[HLC-8120GPC type, Column: Three of TSKgel Multipore HXL-M with guardcolumn, manufactured by TOSOH CORPORATION, Solvent: tetrahydrofuran,Flow rate: 1.0 mL/min., Detector: RI Detector. Column temperature; 40°C., Injection volume: 100 μL] using standard polystyrene as a standardreference material.

Structures of compounds were determined by mass spectrometry (LiquidChromatography: 1100 Type, manufactured by AGILENT TECHNOLOGIES LTD.,Mass Spectrometry: LC/MSD Type, manufactured by AGILENT TECHNOLOGIESLTD.). Hereinafter, the value of the peak in the mass spectrometry isreferred to as “MASS”.

Example 1

Fed were 6 parts of the compound represented by formula (I3-1) and 30parts of chloroform into a reactor, followed by stirring them at 23° C.for 30 minutes. To the obtained mixture, 5.51 parts of1,1′-carbonyldiimidazole was fed and then stirred at 60° C. for 1 hourto obtain a solution containing the compound represented by formula(I3-3). After cooling to 23° C., a mixture of 3.67 parts of3,3-dimethyl-2,4-dioxacyclopentylmethanol and 3.67 parts of chloroformwas dropped over 30 minutes to the obtained solution containing thecompound represented by formula (I3-3), and then stirred at 23° C. for12 hours.

To the resulting reaction mixture, 15 parts of deionized water was addedto wash the reactants, followed by separation. Such washing with waterwas conducted three times.

The extracted organic layer was concentrated by filtration, followed byconcentrating the filtrate to obtain 6.12 parts of the compoundrepresented by the formula (I3-5).

Fed were 5 parts of the compound represented by formula (I3-5) and 27.85parts of acetonitrile into a reactor, followed by stirring them at 23°C. for 30 minutes. After cooling the mixture to 0° C., mixture of 0.31parts of sodiumborohydrate and 3.07 parts of deionized water was droppedover 10 minutes, followed by stirring them at 0° C., for 2 hours. To thereaction mixture, 8.11 parts of 1 N hydrogen hydrochloride was added andthen stirred at 23° C. for 30 minutes, followed by concentration.

To the reaction mixture, 44.56 parts of chloroform and 11.14 parts ofdeionized water were fed and then stirred, followed by separation. Suchwashing with water was conducted three times. The resulting organiclayer was filtrated, and then the resulting filtrate was concentrated.To the concentrated mixture, 37.7 parts of n-heptane was added and thenstirred, followed by removing the supernatant therefrom. The residue wasdissolved in chloroform and concentrated to obtain 3.27 parts ofcompound represented by the formula (I3-6).

The salt represented by the formula (I3-7) was prepared by the methodmentioned in JP2008-127367.

Fed were 3.87 parts of the salt represented by formula (I3-7) and 19.14parts of acetonitrile into a reactor, followed by stirring them at 30°C. for 30 minutes. To the resulting mixture, 1.71 parts of1,1′-carbonyldiimidazole, followed by stirring it at 80° C. for 1 hourto obtain a solution containing the salt represented by the formula(I3-8).

To the solution after cooling to 23° C., a mixture of 3.27 parts of thecompound represented by formula (I3-6) and 3.27 parts of acetonitrilewas fed, followed by stirring it at 80° C. for 12 hours. To theresulting mixture, 38.82 parts of chloroform and 9-7 parts of deionizedwater were fed and then stirred, followed by separation. Such washingwith water was conducted five times. To the resulting organic layer, 1part of activated carbon was added and then stirred at 23° C. for 30minutes, followed by filtration. The filtrate was concentrated and then37.9 parts of tert-buthylmethylether was added thereto, followed byremoving the supernatant therefrom. The residue was dissolved inchloroform and concentrated to obtain 2.96 parts of salt represented bythe formula (I3-9).

Fed were 2.96 parts of the salt represented by formula (I3-9) and 16.8parts of acetonitrile, followed by stirring them at 23° C. for 3Dminutes. To the resulting mixture, a mixture of 0.1 parts of oxalic acidand 0.51 parts of deionized water was added and then stirred at 80° C.for 10 hours, followed by concentration. To the resulting mixture, 40.32parts of chloroform, 10.08 parts of deionized water and 0.3 parts of 28%aqueous ammonia were added and stirred, followed by separation. Suchwashing with water was conducted twice. The resulting organic layer wasfiltrated and then the filtrate was concentrated. To the concentratedmixture, 16.75 parts of tert-buthylmethylether was added and thenstirred, followed by removing the supernatant therefrom. The residue wasdissolved in chloroform and concentrated to obtain 1.09 parts of saltrepresented by the formula (I3-10),

To a mixture of 0.28 parts of the compound represented by formula(I3-11) and 10 parts of chloroform, 0.24 parts of1,1′-carbonyldiimidazole was added and then stirred at 23° C. for 3hours.

To the reaction mixture, 1 part of the salt represented by formula(I3-10) and 10 parts of chloroform were added and then stirred at 23° C.for 1 hour. To the reaction mixture, aqueous potassium carbonatesolution was added and then extraction was conducted with chloroform.The obtained organic layer was washed with deionized water, followed byconcentration.

The residue was dissolved in acetonitrile and then concentrated. To theresulting concentrate, 6.25 parts of tert-buthylmethylether was addedand then stirred, followed by removing the supernatant therefrom.

The resultant residue was dissolved in chloroform, followed byconcentration to obtain 0.78 parts of salt represented by the formula(I-3).

MASS (ESI(+) Spectrum): M⁺ 263.1

MASS (ESI(−) Spectrum): M⁻ 605.2

Example 2

31.8 parts of a solution containing the salt represented by the formula(I3-8) was prepared by the same method as example 1.

To the obtained solution, 1.35 parts of3,3-dimethyl-2,4-dioxacyclopentylmethanol was fed, followed by stirringit at 23° C. for 3 hours. To the resulting mixture, 0.1 parts of oxalicacid and 0.51 parts of deionized water were fed and then stirred at 50°C. for 2 hours, followed by concentration to obtain a solutioncontaining the salt represented by the formula (I2-5).

Mixed were 1.98 parts of the compound represented by formula (I2-6) and30 parts of chloroform, and then 1.65 parts of 1,1′-carbodiimidazole wasadded thereto, followed by stirring the mixture at 23° C. for 3 hours.To the obtained mixture, the solution containing the salt represented bythe formula (I2-5) was added and then stirred at 23° C. for 1 hour.

To the resulting reaction mixture, aqueous potassium carbonate solutionwas added and then extracted with chloroform. The obtained organic layerwas washed with deionized water, followed by concentration.

The residue was dissolved in acetonitrile and then concentrated.

To the resulting concentrate, 20 parts of tert-buthylmethylether wasadded and then stirred, followed by removing the supernatant therefrom.The residue was dissolved in chloroform and concentrated to obtain 2.91parts of compound represented by the formula (I-2).

MASS (ESI(+) Spectrum): M⁺ 263.1

MASS (ESI(−) Spectrum): M⁻ 425.1

Example 3

Fed were 1 part of the salt represented by formula (I3-10) and 10 partsof chloroform, followed by stirring the mixture at 23° C. for 30minutes. To the obtained mixture, 0.14 parts of pyridine was added andthen heated to 40° C.

To the obtained mixture, a mixture of 0.37 parts of the compoundrepresented by the formula (I92-1) and 5 parts of chloroform was droppedover 1 hour, followed by stirring it at 40° C. for 8 hours.

Then to the resulting reaction mixture after cooling to 23° C., 10 partsof deionized water was added, stirred, and separated to collect anorganic layer.

To the reaction mixture, 10 parts of 10% aqueous potassium carbonatesolution at 5° C. was added to wash it, followed by separating into anorganic layer. Then to the collected organic layer, 10 parts ofdeionized water was added to wash it, followed by separating into anorganic layer. Such washing with water was conducted three times. Theobtained organic layer was concentrated and the resultant residue wasdissolved in acetonitrile, followed by concentration. To the resultingconcentrate, 5 parts of tert-buthylmethylether was added and thenstirred, followed by removing the supernatant therefrom. The residue wasdissolved in chloroform and concentrated to obtain 0.38 parts of saltrepresented by the formula (I-92).

MASS (ESI(+) Spectrum): M⁺ 263.1

MASS (ESI(−) Spectrum): M⁻ 647.2

Synthesis of Resin

The compounds used for producing resins were shown as follow.

Hereinafter, the compounds of the formulae are referred to as thesymbols below the formulae. For example, the compound represented byformula (a1-1-2) is referred to as “monomer (a1-1-2)”.

Resin Synthesis Example 1

To a reactor, the monomers (a1-1-3), (a1-2-3), (a2-1-1), (a3-1-1) and(a3-2-3) were mixed in a molar ratio of 30/14/6/20/30 (monomer(a1-1-3)/monomer (a1-2-3)/monomer (a2-1-1)/monomer (a3-1-1)/monomer(a3-2-3)), and 1,4-dioxane was added thereto in the amount ratio of 1.5times weight parts relative to the total weight parts of all monomers toprepare a mixture. To the mixture, azobisisobutyronitrile in the molarratio of azobisisobutyronitrile/all monomers=1/100 andazobis(2,4-dimethylvaleronitrile) in the molar ratio ofazobis(2,4-dimethylvaleronitrile)/all monomers=3/100 were added asinitiators, and the resulting reaction mixture was heated at 73° C. forabout 5 hours.

The reaction mixture obtained was poured into a large amount of amixture of methanol and water (weight ratio=4/1) to cause precipitation,followed by filtrating the mixture to collect precipitates.

The precipitates were dissolved in dioxane, and then the obtainedsolution was poured into a large amount of a mixture of methanol andwater (weight ratio=4/1) to cause precipitation, followed by filtratingthe mixture to collect precipitates. This operation was conducted twicefor purification,

As a result, a resin having a weight-average molecular weight of about8.1×10³ was obtained in a yield of 65%. This resin is called as resinA1. Resin A1 had the following structural units.

Resin Synthesis Example 2

To a reactor (the monomers (a1-1-2), (a1-2-3), (a2-1-1), (a3-1-1) and(a3-2-3) were mixed in a molar ratio of 30/14/6/20/30 (monomer(a1-1-2)/monomer (a1-2-3)/monomer (a2-1-1)/monomer (a3-1-1)/monomer(a3-2-3)), and 1,4-dioxane was added thereto in the amount ratio of 1.5times weight parts relative to the total weight parts of all monomers toprepare a mixture. To the mixture, azobisisobutyronitrile in the molarratio of azobisisobutyronitrile/all monomers=1/100 andazobis(2,4-dimethylvaleronitrile) in the molar ratio ofazobis(2,4-dimethylvaleronitrile)/all monomers=3/100 were added asinitiators, and the resulting reaction mixture was heated at 73° C. forabout 5 hours.

The reaction mixture obtained was poured into a large amount of amixture of methanol and water (weight ratio=4/1) to cause precipitation,followed by filtrating the mixture to collect precipitates.

The precipitates were dissolved in dioxane, and then the obtainedsolution was poured into a large amount of a mixture of methanol andwater (weight ratio=4/1) to cause precipitation, followed by filtratingthe mixture to collect precipitates. This operation was conducted twicefor purification.

As a result, a resin having a weight-average molecular weight of about7.9×10³ was obtained in a yield of 68%. This resin is called as resinA2. Resin A2 had the following structural units.

Resin Synthesis Example 3

To a reactor, the monomers (a1-1-2), (a2-1-1) and (a3-1-1) were mixed ina molar ratio of 50/25/25 (monomer (a1-1-2)/monomer (a2-1-1)/monomer(a3-1-1)) and 1,4-dioxane was added thereto in the amount ratio of 1.5times weight parts relative to the total weight parts of all monomers toprepare a mixture. To the mixture, azobisisobutyronitrile in the molarratio of azobisisobutyronitrile/all monomers=1/100 andazobis(2,4-dimethylvaleronitrile) in the molar ratio ofazobis(2,4-dimethylvaleronitrile)/all monomers=3/100 were added asinitiators, and the resulting reaction mixture was heated at 80° C. forabout 8 hours.

The reaction mixture obtained was poured into a large amount of amixture of methanol and water (weight ratio-4/1) to cause precipitation,followed by filtrating the mixture to collect precipitates.

The precipitates were dissolved in dioxane, and then the obtainedsolution was poured into a large amount of a mixture of methanol andwater (weight ratio=4/1) to cause precipitation, followed by filtratingthe mixture to collect precipitates. This operation was conducted twicefor purification.

As a result, a resin having a weight-average molecular weight of about9.2×10³ was obtained in a yield of 60%. This resin is called as resinA3. Resin A3 had the following structural units.

Resin Synthesis Example 4

To a reactor, the monomers (a1-1-2), (a1-5-1) (a2-1-1), (a3-2-3) and(a3-1-1) were mixed in a molar ratio of 30/14/6/20/30 (monomer(a1-1-2)/monomer (a1-5-1)/monomer (a2-1-1)/monomer (a3-2-3)/monomer(a3-1-1)) and 1,4-dioxane was added thereto in the amount ratio of 1.5times weight parts relative to the total weight parts of all monomers toprepare a mixture. To the mixture, azobisisobutyronitrile in the molarratio of azobisisobutyronitrile/all monomers=1/100 andazobis(2,4-dimethylvaleronitrile) in the molar ratio ofazobis(2,4-dimethylvaleronitrile)/all monomers=3/100 were added asinitiators, and the resulting reaction mixture was heated at 75° C. forabout 5 hours.

The reaction mixture obtained was poured into a large amount of amixture of methanol and water (weight ratio=−4/1) to causeprecipitation, followed by filtrating the mixture to collectprecipitates.

The precipitates were dissolved in dioxane, and then the obtainedsolution was poured into a large amount of a mixture of methanol andwater (weight ratio=4/1) to cause precipitation, followed by filtratingthe mixture to collect precipitates. This operation was conducted twicefor purification.

As a result, a resin having a weight-average molecular weight of about7.2×10³ was obtained in a yield of 78%. This resin is called as resinA4. Resin A4 had the following structural units.

Resin Synthesis Example 5

To monomer (a4-1-7), 1,4-dioxane was added in the amount ratio of 1.5times weight parts relative to the total parts of all monomer to preparea mixture. To the mixture, azobisisobutyronitrile as an initiator in themolar ratio of azobisisobutyronitrile/all monomers=0.7/100 andazobis(2,4-dimethylvaleronitrile) as an initiator in the molar ratio ofazobis(2,4-dimethylvaleronitrile)/all monomers=2.1/100 were added, andthe obtained mixture was heated at 75° C. for about 5 hours. Thereaction mixture obtained was poured into a large amount of a mixture ofmethanol and water (weight ratio=4/1) to cause precipitation. Theprecipitate was collected by filtration, and then dissolved in dioxane,followed by pouring the resultant solution into a large amount of amixture of methanol and water to cause precipitation. This operation wasconducted twice for purification. As a result, a resin having aweight-average molecular weight of about 1.8×10⁴ was obtained in a yieldof 77%. This resin is called as resin X1. Resin X1 had the followingstructural unit.

Examples 4 to 12 and Comparative Example 1

(Preparation of Photoresist Composition)

The following components were mixed and dissolved, further, filtratedthrough a fluorine resin filter having pore diameter of 0.2 μm, toprepare photoresist compositions shown in Table 5.

<Resin (A)>

Resin A1, Resin A2, Resin A3, Resin A4, Resin X1

<Acid Generator>

I-3: The compound represented by formula (I-3)

I-2: The compound represented by formula (I-2)

I-92: The compound represented by formula (I-92)

BI-3: The compound represented by the formula

Z1: The compound represented by formula

<Quencher>

Basic Compound C1: 2,6-diisopropylaniline

<Solvent>

propylene glycol monomethyl ether acetate 265 parts propylene glycolmonomethyl ether 20 parts 2-heptanone 20 parts γ-butyrolactone 3.5 parts

TABLE 5 Acid Basic Resin (A) generator compound PB/PEB (Parts) (Parts)(C) (Parts) (° C.) Ex. 4 A1 = 10 I-3 = 1 C1 = 0.07 100° C./90° C. Ex. 5A2 = 10 I-3 = 1 C1 = 0.07 110° C./100° C. Ex. 6 A2 = 10 I-3/B1-3 = C1 =0.07 110° C./100° C. 0.7/0.3 Ex. 7 A2/X1 = 10/0.7 I-3 = 1 C1 = 0.07 110°C./100° C. Ex. 8 A2/X1 = 10/0.7 I-2 = 1 C1 = 0.07 110° C./100° C. Ex. 9A3 = 10 I-3 = 1 C1 = 0.07 110° C./100° C. Ex. 10 A4/X1 = 10/0.7 I-3 = 1C1 = 0.07 110° C./100° C. Ex. 11 A4/X1 = 10/0.7 I-2 = 1 C1 = 0.07 110°C./100° C. Ex. 12 A4/X1 = 10/0.7 I-92 = 1 C1 = 0.07 110° C./100° C.Compar. A3 = 10 Z1 = 1 C1 = 0.07 110° C./100° C. Ex.1(Preparation of Photoresist Pattern)

Silicon wafers (12 inches) were each coated with “ARC-29”, which is anorganic anti-reflective coating Composition available from NissanChemical Co. Ltd., and then baked at 205° C. for 60 seconds, to form a78 nm-thick organic anti-reflective coating.

Each of the photoresist compositions prepared as above was spin-coatedover the anti-reflective coating so that the thickness of the resultingfilm became 85 nm after drying. The silicon wafers thus coated with therespective photoresist compositions were each prebaked on a directhotplate at a temperature shown in “PB” of the column “TB/PEE” in Table5 for 60 seconds. Using an ArF excimer stepper for immersion exposure(“XT: 1900Gi” manufactured by ASML, NA=1.35, 3/4 Annular, X-Ypolarization), each wafer thus formed with the respective resist filmwas subjected to line and space pattern exposure with the exposurequantity being varied stepwise. At this exposure, a mask which had lineand space pattern of 40 nm and a single dummy pattern of 42 nm set atthe corner of the line and space pattern was used. Ultra pure water wasused for immersion solvent.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at a temperature shown in “PEB” of the column “PB/PEB” inTable 5 for 60 seconds and then to paddle development for 60 secondswith an aqueous solution of 2.38 wt % tetramethylammonium hydroxide.

Effective Sensitivity (ES) was expressed as the exposure quantity thatthe line width of the line and space pattern of 50 nm became 1:1 afterexposure through line and space pattern mask.

Evaluation of Pattern

The line and space pattern of 50 nm on the obtained film at the exposurequantity equal to the effective sensitivity was observed with a runningelectron microscope. The pattern whose top and bottom are rectangularshape as shown in FIG. 1 (a) was determined as ◯. The pattern whose topand bottom are a round shape as shown in FIG. 1 (b) was determined as X.The results are shown in Table 6.

Evaluation of Optical Proximity Correction

The dummy pattern of 50 nm on the obtained film was observed with ascanning electron microscope.

The case where the dummy pattern was not existed on the film wasdetermined as ◯. The case where the dummy pattern was existed partly ortotally on the film was determined as X.

The results are shown in Table 6.

TABLE 6 Dummy Shape pattern Ex. 4 ◯ ◯ Ex. 5 ◯ ◯ Ex. 6 ◯ ◯ Ex. 7 ◯ ◯ Ex.8 ◯ ◯ Ex. 9 ◯ ◯ Ex. 10 ◯ ◯ Ex. 11 ◯ ◯ Ex. 12 ◯ ◯ Compar. X X Ex.1

Specifically, it was confirmed that the photoresist compositions ofExamples 7, 8, 10, 12 and 12 can provide photoresist pattern with fewdefects among the photoresist compositions of Examples,

Since the photoresist composition of the present invention comprises asalt of the present invention, the photoresist composition can provide aphotoresist pattern which is accurate, and which is free from a dummypattern used for optical proximity correction even in case of conductingoptical proximity correction with a dummy pattern, as apparent from theabove-mentioned examples. The salt and the photoresist pattern of thepresent invention are suitable for semiconductor microfabricationemploying lithography process.

What is claimed is:
 1. A salt represented by formula (I):

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group, the moiety L¹-OH of formula (I) isrepresented by formula (L¹-1):

wherein X⁰ represents a single bond, a C1-C14 divalent aliphatichydrocarbon group which can have a fluorine atom or a hydroxyl group, ora group represented by formula (a-1):-A¹⁰

X¹⁰-A¹¹

_(s) X¹¹-A¹²-*  (a-1) where s represents an integer of 0 or 1, X¹⁰ andX¹¹ each independently respect an oxygen atom, a carbonyl group, acarbonyloxy group, or an oxycarbonyl group, A¹⁰,A¹¹ and A¹² eachindependently represent a C1-C12 divalent aliphatic hydrocarbon groupwhich can have a fluorine atom or a hydroxyl group, * represents abinding position to a corbon atom, X¹ represents —O-*¹, —NR²-*¹,—O—CO-*¹, —O—CH₂—CO—O-*¹ or —NR²—CH₂-*¹ where *¹ represents a bindingposition to W, *⁰ represents a binding position to a carbon atom bindingto Q¹ and Q², and m¹ represents an integer of 0 to 6, W represents aC3-C36 alicyclic hydrocarbon group in which a methylene group can bereplaced by an oxygen atom, a sulfur atom, a carbonyl group or asulfonyl group, and in which a hydrogen atom can be replaced by ahydroxy group, a C1-C12 alkyl group, a C1-C12 alkoxy group, C3-C18alicyclic hydrocarbon group or C6-C14 aromatic hydrocarbon group, and Z⁺represents an organic cation.
 2. The salt according to claim 1, whereinthe X¹ represents —O-*¹, —NR²-*¹, —O—CO-*¹,—O—CH₂-*¹, or —NR²—CH₂-*¹where *¹ represents a binding position to W.
 3. The salt according toclaim 1, wherein Z⁺is an triarylsulfonium cation.
 4. A photoresistcomposition, which comprises the salt according to claim 1 and a resinwhich is hardly soluble or insoluble but soluble in an aqueous alkalisolution by action of an acid.
 5. The photoresist composition accordingto claim 4, which further comprises a basic compound.
 6. A process forproducing a photoresist pattern comprising the following steps (1) to(5): (1) a step of applying the photoresist composition according toclaim 4 on a substrate, (2) a step of forming a photoresist film byconducting drying, (3) a step of exposing the photoresist film toradiation, (4) a step of baking the exposed photoresist film, and (5) astep of developing the baked photoresist film, thereby forming aphotoresist pattern.